| With the accelerated process of urbanization,cities are highly developed and have been expanding,megacity is formed and even showing the characteristics of regional urban agglomeration.Megacity is threatened seriously by flood disaster.A research on evaluation of flood disaster scenario of megacity and application in Taihu basin is of great theoretic and practical value,for improving the system of urban disaster prevention and mitigation,as well as the capacity of urban flood control and drainage.On the basis of the composition and characteristics of urban flood disaster,the evaluation index system of megacity flood disaster scenario is conducted,and optimized evaluation models of the flood disaster scenario are built.Evaluation of megacity flood disaster scenario and the application research on flood disaster scenario assessment and prediction of urban agglomeration in Taihu basin are carried out.The main contents are as follow.(1)The composition of urban flood disaster is comprehensively analyzed from three aspects: the current features,evolution characteristics and the causes of megacity flood disaster.The urban flood disaster presents some such characteristics as great loss,high suddenness,variable loss feature and increasing flood disaster risk.The evolution characteristics include mechanism of generation,domino reaction and mutagenic effect of affected system.The causes of flood disaster are analyzed based on three aspects of nature,society and disaster administration capacity,facilitating further understandings of urban flood disaster characteristics and providing theoretical guidance for the construction of urban flood control and drainage.(2)The features of megacity flood disaster scenario evaluation and design principles of index system are analyzed.The evaluation index system is designed on the basis of overall consideration of flood,waterlogging,flood control and drainage facilities,socio-economic elements,ecological environment,disaster management,emergency relief and post-disaster reconstruction.The method of index value determination and standardization is introduced and realized.(3)The basic principle and implementation approach of urban flood disaster evaluation are discussed based on Entropy-weight TOPSIS method and reformative principal component analysis method according to the former one,contributing to both the design of optimized megacity flood disaster scenario evaluation model and the refinement of correlative theory system.(4)With the application of optimized evaluation model based on Entropy-weight TOPSIS method and principal component analysis method,17 scenario evaluation indexes are selected to evaluate 21 cities’ capacity of flood disaster prevention and mitigation comprehensively sorted according to results of the evaluation.(5)Megacity always develops in the form of urban agglomeration,such as urban agglomeration of Taihu basin,chosen as a typical study object.The joint distribution model of the exceeding limited water level and the occurrence time of typhoon in Taihu is constructed by using the Copula function,sets up a joint probability calculation model,and quantifies the encounter probability of exceeding limited water level,astronomical tide and typhoon.Through the simulation of flood disaster scenario according to high tide level,high water and typhoon,13 scenario evaluation indexes on basis of realistic situation are selected.Combined with these 13 indexes,optimized evaluation model based on Entropy-weight TOPSIS method and principal component analysis method is applied to evaluate the disaster situation.And forecasts the future social and economic development of the urban agglomeration in Taihu basin,assesses the future disaster scenarios and quantifies the expected losses of the 2030 and 2050 years,contributing to improve the disaster prevention and mitigation capacity of urban agglomeration of Taihu basin. |
