Abstract: This paper aims to investigate key issues related to simulating floods from hilly to plain areas due to human activities and propose corresponding solutions and models. These issues encompass the uneven spatial distribution of rainfall within the basin, substantial differences in runoff generation and convergence between hilly and plain areas, and complex boundary conditions influenced by water conservancy engineering construction and scheduling. To address these issues, the Hanbei River basin is divided into 11 units as a case study. The uneven spatial distribution of rainfall is tackled by analyzing the spatial distribution of extreme rainfall events in each unit. Calibration of each unit’s hydrological model parameters is conducted based on its underlying surface conditions using the API model, thereby improving the model’s fit to the actual conditions and addressing the significant differences in runoff generation and convergence between hilly and plain areas. The model incorporates the impacts of human activities such as river diversion, reservoirs, flood storage areas, sluices, pump stations construction, and scheduling, as well as land use, into the physical model and runoff simulation. This integration enables the construction of a runoff system that accurately reflects actual scheduling scenarios. The NSE values of simulated peak flows for all scenarios exceed 0.85, indicating strong agreement between simulated and measured values for peak flow, water level, and peak time.

Key words: simulation of heavy rain and flooding, coupled hydrological and hydrodynamic model, Hanbei River basin, influence of human activities