Alternating iterative coupling of hydrological and hydrodynamic models applied to Lingjiang river basin, China

Abstract The increasing frequency of extreme-weather flood events is attributable to climate change. In addition to constructing basic water conservancy facilities, predicting the flood inundation range is important for preemptively reducing the flood risk and guiding the formulation of government policies. Conventionally, flood routing simulation based on two-dimensional hydrodynamic simulation is applied. However, the hydrological method has inherent advantages, which can be leveraged to realize information exchange. In 2019, Typhoon Lekima caused a severe flood disaster in Taizhou, China and large-scale inundation in residential areas. In this study, this event is hydrologically and hydrodynamically modeled using HEC-WAT and other HEC platform software. Loose coupling and tight coupling are conducted via different coupling methods, and the differences between the two modeling methods are compared. It is found that tight coupling utilizes the dynamic interaction mechanism of the hydrological and hydrodynamic models, which reduces the simulation error. Similarly, the flood problem in the Taizhou area is analyzed. The two-dimensional flood routing simulation results show that the flood flows in the plain areas along the bank are within the flood area, the maximum depth of inundation in the area reaches 17.0 m, and the water level reaches 11 m. The comparative simulations show that the alternating iterative coupling of hydrological and hydrodynamic can improve the accuracy of the model simulation results.