Assessment And Improvement Of Urban Flood Resilience

The rapid urban development in China has led to an increase in the frequency of flood disasters,which seriously threaten urban ecological security and human life.Urban flood resilience（UFR）is important for urban safety and stability,as an important focus of urban resilience construction.However,the previous urban flood simulation still lacked analysis covering the full cycle processes.There were relatively few studies on the UFR assessment based on changes of the whole system state.To comprehensively evaluate urban system performance during the entire processes of rainfall,runoff,flooding,and drainage,a systematic framework was developed for UFR assessment covering runoff simulation,flood estimation,and resilience assessment,with the principal parameters of the inundated urban proportion and total simulation time.Because the extent of urban flooding can be influenced by climate change and the rate of urbanization,this study chose the corresponding representative factors of precipitation and infiltration rate,described by 21 simulation scenarios（S1-S21,seven rainfall return periods and three infiltration rates）to quantify UFR according to urban system performance.The priority regions were identified based on UFR values and Geo SOS model.The effectiveness of the proposed framework was demonstrated in application to a typical highly urbanized area（i.e.,Dongguan,China）.The following results were derived:（1）The systematic framework can achieve the quantification of UFR in large-scale flood disasters,overcome the scale defects of resilience assessment,and be applicable to other regions and cities.It overcomes the problem in quantifying large-scale flood disasters due to lack of pipe network data.Furthermore,the system performance curve was used to dynamically describe the different stages of urban resistance,adaptation,and recovery for flood disasters,when supplementing the simulation of the infiltration rates of the urban underlying surface.（2）At the urban scale,the minimum and maximum urban inundation areas for the 21 scenarios would be 58.8 and 288.5km²,respectively.At the district scale,the regions,most severely affected by the flood,were Shuixiang New City and Urban area district.Conversely,the Linshen area and Eastern Industrial Park area experienced less severe flood due to their higher proportion of ecological land.At the subcatchment scale,the 1^st located in Zhongtang town and 3^rd located in Gaobu town subcatchment were most severely affected,with inundation proportion of 62%and53%,respectively.（3）At the urban scale,the UFR values under the 21 scenarios would be0.9494-0.9863,locating at the high and very high level.At the subcatchment scale,the minimum and maximum values of UFR were 0.6552 and 1,respectively.The rainfall return period was the main factor influencing UFR under relatively short rainfall return periods（i.e.,S1-S9）,while infiltration rate was the principal influencing factor under relatively long rainfall return periods（i.e.,S10-S21）.（4）Under the 21 scenarios assessed for UFR,18 subcatchments with the high inundation and low recovery under S19 were chosen as the improvement regions.The two scenarios of UFR impact factors and social economic development were set to identify the improvement sequence.Based on the results,the 8^thsubcatchment located in Shijie town was regarded as the highest priority area in the social economic development scenario due to its highest population density and GDP.However,the spatial distribution characteristics of the priority area between the UFR impact factor scenario and social economic development scenario were significantly different.This study proposed a systematic framework for assessing urban resilience under flood scenarios,and established a resilience simulation and evaluation system that integrates“resistance-adaptation-recovery”.This framework provides a new perspective for assessing urban resilience at a large-scale and has important implications for informing policies related to flood disaster prevention,urban development goals,and regional management.