Study on the bidirectional coupling 1-D and 2-D model of urban flood based on different flow exchange modes

In order to accurately simulate the urban flood process, the bidirectional coupling hydrodynamic model of urban surface and underground sewer flow was constructed based on 1-D pipe network of SWMM and 2-D urban surface model, considering three exchange modes of surface runoff and underground pipe flow. The coupled model was firstly verified by flume experiment and theoretical case studies. Then the coupled model was applied to an urban street block in Glasgow, UK, to analyze the effects of drainage network and different exchange modes of surface and underground flow on urban flooding process. The results show that:the coupled model has good precision and reliability in simulations of flume experiment and theoretical case, which can accurately simulate the urban flooding process with drainage pipe network being included. The three exchange modes of surface and underground flow were considered in urban flooding simulation of Glasgow, including the manhole-based approach, the inlet approach and the inlet-manhole approach. Compared with the case without drainage system, the simulated maximum inundated area obtained from these three flow exchange modes respectively were reduced by 9.3%, 23.2% and 24.5%, in which the reduction effect of high inundation degree was more significant, and the inundation area were reduced by 43.6%, 79.9% and 80.9% respectively. The reduction effect of water depth and inundated area by using the manhole-based approach was much smaller than that of the inlet approach and the inlet-manhole approach, and the difference between the inlet approach and the inlet-manhole approach was small. Moreover, the inlet approach and the inlet-manhole approach are relatively accordance with the actual situation, and the inlet-manhole approach is simpler and more computationally efficient. Therefore, using the inlet-manhole approach is more suitable than others in the exchange process of surface runoff and underground pipe flow.