An Improved Coupled Hydrologic-Hydrodynamic Model for Urban Flood Simulations Under Varied Scenarios

Cities place a high priority on addressing urban flooding issues and have worked on flood prevention planning and construction efforts. This study aims to develop the improved coupling hydrologic-hydrodynamic model based on SWMM and TELEMAC-2D model by considering river runoff factors. Taking Tongzhou district of Beijing as an example, two different coupled models of the drainage network are constructed for comparison. The research focused on the drainage capacity of the study area and surface ponding water under different rainfall recurrence periods to evaluate the current flood resilience status and the priority of drainage network improvements. The results indicate that the demonstration area effectively mitigates urban flooding and can handle a 100-year return period rainfall event, with a maximum inundation depth of 0.407 m and an overflow node ratio of 20.8%. As the rainfall recurrence period increases, the number of overflow nodes tends to stabilize. Due to the high susceptibility of traffic hubs in cities to flooding, the result of contrast model analysis suggests prioritizing the drainage networks under main roads and overpasses and implementing Low Impact Development (LID) facilities around rivers to enhance urban infiltration and reduce river overflow risks. This coupled model demonstrates good applicability and high simulation accuracy for complex urban flood scenarios, emphasizing the importance of targeted urban planning and infrastructure improvements in enhancing flood resilience.