Assessing the effects of sponge city construction in Beijing with an improved coupled hydrologic-hydrodynamic model

Abstract Low Impact Development (LID) theory represents a new paradigm for sustainable urban development, focusing on enhancing stormwater management, mitigating urban flooding, and reinforcing urban planning. In this study, we select Tongzhou District in Beijing as study area, establish an improved coupled hydrologic-hydrodynamic model based on SWMM and TELEMAC-2D model that integrates the dynamics of surface, pipeline networks, and river channels through one-way coupling method. The drainage capacity of pipe network and surface inundation under rainfall during different recurrence periods were simulated and analyzed. The results show that the concept of LID, also known as sponge city transformation in China, offers significant flood mitigation benefits for the megacities. As rainfall return periods increase, the number of overflow nodes and overloaded pipelines is observed by increase rapidly and become stable in study area. Specifically, under 100 year return period rainfall scenario, the original model projected a maximum inundation depth of 0.407m and an overflow node proportion of 20.8%. Through the comparison simulation result of coupling model suggest prioritizing the reconstruction of pipelines under the first-grade roads and overpasses, followed by LID rebuilding around the river to effectively increase urban infiltration rate and mitigate river overflow risks.