Risk Assessment and Management Method of Urban Flood Disaster

Due to the failure of flood control and drainage infrastructure to match the rapidly growing urbanization process, urban flooding has become one of the most significant disasters faced today. It is essential to carry out the risk assessment of flood scientifically and study the optimal allocation of stormwater infrastructure in-depth. In this paper, a complete urban flooding risk assessment and management methodology is proposed by linking "scenario simulation", "risk assessment" and "allocation optimization", which is applied in Xiaozhai area of Xi'an, China. Based on the measured data and the results of the maximum water depth survey, an accurate coupled model of flooding in the study area was established, which was used to simulate the current situation and design scenarios. On the basis of the "hazard-vulnerability" framework, a multi-factor flood risk levels were assessed, and four risk gradations were mapped. Taking the results of risk analysis as the point of view, the allocation-effect functions are fitted by the polynomial curves and consisted as a part of objective function. Then, the optimal scenario is obtained by NSGA-III. The results show that the urban flood risk zoning is accurately screened, and the optimal scenario increases the runoff control rate from 54 to 85% compared with the traditional development scenario. The regional risk-free area doubles, the low-risk and medium-risk areas are reduced by a factor of 2 and 16, and the high-risk are all eliminated, with significant flood control effects. The cost savings are 127 million CNY compared to the initial scenario without optimization. The overall idea starts from flood formation, which provides a research method that can be applied to regions with similar problems.