Assessment of Flood Inundation by Coupled 1D/2D Hydrodynamic Modeling: A Case Study in Mountainous Watersheds along the Coast of Southeast China

Mountain flood disasters in China's southeastern coastal watershed are not predictable and are sudden. With rapid urbanization and development in the middle and lower reaches of the region, the accumulation of wealth and population has magnified the flood risk. Exploring flood numerical simulation technology suitable for the rapid economic development of mountainous basins, effective flood models are the key tools for controlling and mitigating flood disasters. In this paper, we established a 1D/2D real-time dynamic coupling hydraulic model, aimed at exploring the applicability of the model in flood simulation of mountainous river basins with rapid economic development. The Luojiang River Basin (Huazhou Section) in Guangdong Province was used as the case study. The model's ability was validated against the 22 July 2010 and 14 August 2013 inundation events that occurred there. The simulation results show that the output of the flood model is highly similar to the observation and survey results of historical flood events. The research results prove that the 1D/2D coupling model is not only an applicable tool for exploring flood spread characteristics such as flood range, velocity, depth, arrival time, and duration, but also can feed back the impact of water conservancy projects such as dikes on flood spread in the basin. It is of great significance to effectively guide the comprehensive design and management of subsequent wading projects in mountain river basins, and to improve flood prevention and disaster reduction capabilities in mountain areas.