Study On Urban Flood Risk Management And Practical Technology

Along with the rapid urbanization in China in recent decades, urban flood disaster system, involving disaster-forming environment, hazards, receptors and prevention capacities, is being sharply changed. Some new features of flood disaster appear in urbanized areas, which bring a series of challenges to urban flood control and disaster mitigation. In order to cope wisely with the new urban flood disaster, it is necessary to carry forward flood risk management strategies. Meanwhile, flood simulation model would serve as a useful tool in formulating and implementing the flood risk management strategies.According to current situation in flood risk management researches, the current flood risk management strategies can be divided into three categories, i.e. regulating and controlling strategies for flood hazard, adapting strategies and emergency response strategies for adaptive capacities of human being against flooding. In order to comprehensively promote the three major strategies of urban flood risk management, Fuzhou city of China was taken as a pilot city to make the study in this thesis. A numerical model had been established for urban flood simulation at first, and then information requirements analysis were carried on for different categories of flood risk management measures. Based on which, simulating schemes and corresponding calculation conditions could be selected more effectively for urban flood risk analysis and assessment, that improved the practicability of the urban flood simulation model in flood risk management. Finally, combining with the practical techniques of flood risk analysis and specific practices of improving urban flood management in the pilot city, proper flood risk disposal and mitigation measures were studied and discussed to cope with new challenges in urban flood disaster, which provides a referential example for other cities in carring out flood risk management. The main research methods and conclusions are as follows:(1) Based on recent advances in runoff yield and conflux research, SCS model proposed by U.S. SWCB (Soil and Water Conservation Bureau) and urban flood simulation technique developed by IWHR were combined to establish a numerical model for urban flood simulation. The model was calibrated and validated by means of the observed data of heavy rainstorm and flooding in Fuzhou caused by typhoon Longwang and Bilis in2005and2006, respectively. Several calculation schemes, involving flood scenarios with high possibility or the most dangerous situations, were designed in the study. The calculation schemes were simulated by using the numerical model, and the results show that the model can provide the flooding information in urban area, such as extent of the inundated areas and duration, distribution of the maximum water depth and velocities; and the proposed model also has been proved with acceptable accuracy and good stability. The underlying surface data and hydrological data of five different years (1989,1994,2001,2006and2010) in Fuzhou city were obtained according to the observation data and reasonable assumptions, and urban flood numerical models of five different years were set by utilizing the obtained data. Evolution of flood characteristics during the five different periods was analyzed quantificationally by using the simulated results of five years. The total inundated areas of the designed scheme showed a trend of increase, and the average change rate of inundated areas with different levels of water depth was positively correlated with the average change rate of the urban impermeable surface areas.(2) In view of diversified demands from flood hazard mapping in China, study of flood hazard mapping that serve different purposes (such as flood risk management, flood prevention direction, human activities normalization and risk awareness of public) was carried out. A multi-layer mapping method was proposed in the study, and flood hazard mapping was divided into three layers, which include the inundated mapping, flood hazard forecasting mapping and flood risk assessment information. The informations that were used for making flood hazard mapping, involving past inundation information, flood hazard forecasting information and flood risk assessment information, were discussed according to the design principle of multi-layer flood mapping. Urban flood simulation model was used to make information for the flood hazard mapping, and caculation conditions of the model, including initial conditions, boundary conditions and run control mode, could be properly selected according to the purpose of flood hazard mapping. Fuzhou city was taken as the case to make study of flood hazard mapping for drainage plan in the thesis, and flood risk analysis of current drainage system and planning drainage system in2020was carried out by using the numerical model, and then flood hazard mapping of current drainage system and planning drainage system in2020were made on the basis of flood risk analysis. Benefit assessment of planning drainage system in2020was carried out depending on flood hazard mapping. (3) Vulnerability of urban receptors in flood prevention is rising during the rapid urbanization, and emergency response strategies were introduced to strengthen the capacity of urban flood prevention and flood disaster response. Emergency plan for flood control, which is considered as one of the most important emergency response strategies, was studied in this thesis, and flood simulation technique was applied in urban flood warning and emergency response to improve the practicability and operability of the Emergency plan. Referring to achievements of flood warning at home and abroad, a set of proposed flood warning standard that involves early flood warning standard and flood warning standard of inundated area was made and introduced to Fuzhou city in this study. Several calculation schemes, involving flood scenarios with high possibility or the most dangerous situations,, were designed for the case study, and then the calculation schemes were simulated by using the numerical model, and study of flood warning and emergency response was carried out on the basis of flood simulation results; and proper flood risk mitigation and emergency disposal measures were designed in the emergency plan.(4) Fuzhou city was taken as the case to make countermeasures study on flood control and disaster mitigation in the thesis, and the countermeasures that involve rainwater harvesting, rainwater utilization and urban waterlogging regulation, were introduced to Fuzhou city in the study. According to the standard of national flood retention, a set of roof rainwater harvesting system was designed for Fuzhou city, and effect evaluation of rainwater harvesting was carried out by using urban flood simulation model. Urban pluvial flood regulation measures that include flood storage of Qinting Lake and reservoir regulation were designed for Fuzhou city, and effect evaluation of the measures was carried out by using urban flood simulation model. The evaluation results could be served as technical support for flood disaster mitigation.