Evaluation And Improvement Strategy Of Urban Flood Resilience

Although cities account for only 2% of the world’s land area,they carry nearly half of the world’s population,70% of the GDP,greenhouse gas emissions and waste,and 60% of energy consumption.Climate change and human activities directly affect the temporal and spatial distribution characteristics of the water cycle elements,making floods more frequent and severe.The disastrous consequences are often concentrated in urban areas and severely affect urban development and residents’ lives.This has become a global issue that urgently needs to be addressed.To this end,the Chinese government has issued a series of policies to deal with the problem of urban flood disasters.However,traditional flood disaster management measures and disaster prevention and reduction systems still have room for optimization and improvement.With the introduction of the concept of resilience,the Chinese government clearly requires the construction of resilient cities in the 14 th FiveYear Plan to improve the ability of cities to withstand disasters.Resilient city is highly expected by the world because of its emphasis on coexisting with risks,improving the ability of cities to respond to crises,and more in line with the needs of risky society under increasingly urban floods.Scholars have conducted a lot of explorations on urban resilience,but the research on the combination of urban flood disasters and urban resilience is still in the exploratory stage.There is a lack of vertical and horizontal comparisons of urban flood resilience,and the coupling and coordination relationship within urban resilience.There are also fewer scenario simulations considering future climate change,and there is a lack of targeted improvement strategies suitable for conditions in China.Therefore,this study integrates the urban "social-economic-natural composite ecosystem" theory and "pressurestate-response" model.The cities in the Yangtze River Delta region are selected to conduct the evaluation.The paper aims to explore the quantitative evaluation and improvement strategies of urban flood resilience.The specific research contents are carried out according to the following steps:(1)Comprehensive analysis of the concept of urban flood resilienceThrough literature review and flood disaster cases,the concept of urban flood disasters is defined,combining its hazard factors,disaster-generating environment and disaster-bearing bodies.The causes,effects and governance methods of urban flood disasters are deeply analyzed.Combining existing research on urban resilience,the concept,characteristics and framework of urban resilience are defined and discussed.On this basis,the concept of urban flood resilience in this research is proposed,and its characteristics and applicable research framework are analyzed.(2)Establishment of evaluation framework for urban flood resilienceBased on the concept and connotation of urban flood resilience,the theory of urban "socialeconomic-natural composite ecosystem" and the "pressure-state-response" model are combined to analyze the relationship between pressure resilience,state resilience and response resilience in urban flood resilience formation mechanism.On this basis,a systematic review method is used to select relevant indicators to construct a PSR-SENCE evaluation index system for urban flood resilience,and all indicators are divided into three types: statistics,calculations and evaluations.Combining the research area,the final evaluation index system applied to the resilience of cities in the Yangtze River Delta are established to lay the foundation for subsequent measurement.(3)Quantitative evaluation of urban flood resilience in the Yangtze River DeltaBased the PSR-SENCE evaluation framework of urban flood resilience,the weight of each indicator is determined by a combination of subjective and objective methods,and the VIKOR method is selected to conduct static evaluation of 27 cities in the Yangtze River Delta.Then the urban flood resilience of 2019 is obtained.On this basis,by analyzing the changes in time,space and region of urban flood resilience in the past five years,a dynamic assessment of cities in the Yangtze River Delta region is carried out,and the urban flood resilience and its three-dimensional spatial pattern are explored.(4)Dynamic simulation of the improving-scenario of urban flood resilienceBased on the evaluation results of urban flood resilience,a SD simulation model of urban flood resilience is designed,and the F-DEMATEL method is used to clarify the causal logic relationship within the urban flood resilience system.The system causal flow diagram is drawn,and the system dynamics simulation model is constructed.On this basis,five simulation scenarios(current status continuation,economic priority,social priority,natural priority,and coordinated development)are designed under the background of climate change.Shanghai is selected as an example city to adopt the simulation model with multiple scenarios.Then,the optimal path to improve the urban flood resilience can be obtained.(5)Exploring the theoretical strategies for improving urban flood resilience considering coupling and coordinationWith the help of "social-ecological" system analysis framework,various components of the social economic system and natural ecosystem in the urban system are identified and their interaction are discussed.On this basis,the coupling and coordination model is used to quantify the coupling and coordination relationship between the three-dimensionality of urban flood resilience for the cities in the Yangtze River Delta region,as well as the time-space analysis.Furthermore,in order to explore the reasons for the imbalance of each dimension,influencing factors are selected and spatial measurement methods to analyze the internal and external influence mechanism of urban flood resilience coupling and coordination are adopted.(6)Refining practical strategies to improve the urban resilience of cities in the Yangtze River DeltaCombining the aforementioned results of static and dynamic evaluation,scenario simulation,and coupling and coordination analysis,the shortcomings and deficiencies of urban flood resilience in the Yangtze River Delta are found out.Then,the process model of policy analysis is used to sort out the relevant policies for urban flood resilience in the Yangtze River Delta to clarify the current situation and practice status.On this basis,the agenda setting,formulation process and implementation institutions are discussed with three major international cities(or countries),which are New York,London,and Singapore.Furthermore,an overall improvement strategy for urban flood resilience is suggested from region,province,and city level respectively.And specific improvement strategies from the pressure dimension,state dimension,response dimension and coupling coordination are also proposed.This study put forwards the concept of urban flood resilience,and establishes an urban flood resilience assessment framework.It is applied to the cities in the Yangtze River Delta region,and the impact mechanism,scenario simulation and policy analysis are conducted to explore the improvement path and strategies.The framework established in the paper can help to deepen the researches in urban resilience and flood mitigation.The strategies put forward in the paper can help to improve urban flood resilience in the Yangtze River Delta at a macro level.