Risk Assessment Of Flood Disasters In The Middle-Lower Reaches Of The Yangtze River

The middle-lower reaches of the Yangtze River is one of the areas with the most severe floods in China.Its social and economic development is strongly affected and constrained by flood disasters.With the global warming,the risk of flood disasters in the Yangtze River Basin has an increasing trend.The assessment of flood disaster risk in the middle-lower reaches of the Yangtze River is of great significance for strengthening comprehensive risk prevention and mitigation of disaster losses.The natural and social attributes of the study area are comprehensively considered.Based on the hazard of natural environment,social vulnerability and the exposure of hazard bearing bodies in the middle-lower reaches of the Yangtze River,the flood risk of the study area was studied and a framework of evaluation models is constructed.In terms of flood hazard,we examined the hazard of disaster causing factors and the environmental sensitivity,and selected five indicators:average annual extreme precipitation,average annual extreme precipitation frequency,drainage network density,relative elevation,and standard deviation of elevation.We used the analytic hierarchy process to determine index weights and calculated hazard for floods.In terms of social vulnerability,referring to the US SoVI model method construction index system,we comprehensively considered 27 indicators that affect the social vulnerability covered by social economy,collected county-scale socio-economic statistical data for analysis and inspection,and calculated comprehensive social vulnerability index.In terms of the exposure of disaster-bearing bodies,we used overlay analysis of land cover data and nightlight data to determine the level of flood exposure in the study area.According to these three indexes,we comprehensively calculated the flood risk scores in the study area,conducted risk zoning,and proposed disaster prevention and reduction recommendations.The study found that the area with the highest risk of flood disaster accounted for 7.52%of the study area,which was mainly concentrated in the northern plains of Jiangxi.It was also distributed sporadically in eastern Hubei and western Anhui;the higher-risk area accounted for 14.40%of the study area and was at high risk.The outskirts of the area are located in the Lancang River basin in Jiangxi Province,southwestern Hubei Province and western Anhui Province.The terrain is dominated by hills and river valleys;the medium-risk area accounts for 29.35%of the research area,including the western part of Jiangxi,most parts of Hunan,the eastern and western parts of Hubei,and Anhui The central region is dominated by mountainous areas;the lower-risk areas account for 28.61%of the study area,mainly distributed in central Hubei,eastern Anhui,northern Zhejiang,and parts of Hunan;low-risk areas account for 20.11%of the study area,mainly located in the delta plains in the lower reaches of the Yangtze River and mountains in northwestern Hubei.On this basis,a global and local spatial autocorrelation analysis was conducted to explore the flood risk agglomeration situation in the study area,and it was found that the flood disaster risk score showed a strong spatial positive correlation.The northern and eastern parts of Jiangxi are high-high clustered areas,and the level of flood risk is high and there is a clear spatial agglomeration phenomenon.It is necessary to strengthen risk prevention and change this pattern as soon as possible.