Study On Improved Urban Flood Risk Assessment Model And Adaptive Disaster Prevention Decision

Urban flood risk assessment is an important tool for urban flood disaster management.The current research mainly considered the area itself as the evaluation object.As the basis of all social and economic activities in a city,urban road network is easily affected by floods.However,most studies that consider the risk assessment of the road environment only considered the road itself as the evaluation object and did not consider potential regional system risks such as traffic congestion caused by road inundation at present.Based on this,this study proposes a spontaneous-triggered risk assessment conceptual model,and applies this model to Haidian Island in Haikou City.According to the risk assessment results,the adaptive disaster prevention measures based on multi-attribute bilateral matching model are proposed and the disaster reduction effects are analyzed.The main research contents and conclusions include:(1)A spontaneous-triggered risk assessment model for urban flood is proposed.Based on considering the spontaneous risk caused by the subregional disasters and socio-economic exposure,the increase of the vulnerability in the subregions associated with it caused by the flooding of the roads in the assessed subregion is quantified as the triggered risk of the assessed area.The spontaneous risk indices maximum mean inundation depth(MD),proportion of the maximum inundation area(PA),maximum mean flow velocity(MV),population density(DPP),POI density(DPOI),building density(DB),and the triggered risk indices maximum mean inundation depth of road(RMD),maximum inundation duration of road(RID),road betweenness centrality(RBC),and number of road bus lines(RBL)are selected to construct the multi-indices system.An urban flood risk evaluation method based on combined weights-gray fuzzy is proposed.This model fills in the shortcomings of secondary risks caused by physical connections between subregions that are not considered in traditional flood risk assessment,and lays the methodological cornerstone for the subsequent urban flood risk assessment.(2)Based on the established spontaneous-triggered risk assessment model,the comprehensive assessment of urban flood risk is carried out with Haidian Island in Haikou City as the evaluation object.First,the indices data is obtained based on the PCSWMM model,big data,satellite remote sensing,network analysis and other technologies.Through spatial analysis,each index is quantified in units of blocks.Secondly,combining the analytic hierarchy process(AHP)and the improved entropy method to calculate the combined weight of each index,and using the gray fuzzy comprehensive evaluation method to calculate the risk value in each subregion.Finally,the natural breakpoint method is selected to classify the flood risk level,and the One at a time(OAT)method is selected to analyze the sensitivity of the evaluation results to changes in indices weights.The results indicate that,compared with the traditional spontaneous risk,the highest and higher risk subregions are more concentrated in the study area center,and the risk of the outer ring subregions is reduced overall after considering the triggered risk.The research results help to identify high-risk areas of urban flood more comprehensively and accurately,and help decision-makers to carry out more targeted urban flood remediation.(3)In view of the lack of current urban flood adaptive disaster prevention decisionmaking models,this study proposes a framework for urban flood management strategy formulation and selection based on a multi-attribute bilateral matching model to simultaneously realize the double matching of measures’ disaster mitigation capabilities with regional risk factors,measures construction needs and regional site conditions.The framework mainly includes four steps: preliminary screening of measures,establishment of the multi-attribute bilateral matching model,appraisal of adaptability of disaster prevention measures,program simulation and analysis of disaster reduction effects.Based on the risk assessment results in Chapter 3,the framework is applied using Haidian Island as an example.The results show that after the implementation of the plan,the reduction rates of submerged area and submerged volume in the highest risk areas are 11.6% and 20.8%,respectively,which are both higher than the 10%treatment target.The adaptive disaster prevention measures decision-making model based on the multi-attribute bilateral matching model proposed in this study can make full use of the limited disaster prevention capabilities of green measures.However,if the risk is to be truly reduced,measures such as grey and blue infrastructure and urban emergency management must be combined.