Study On Risk Zoning Of Highway Flood Disasters In The Chinese Mainland

Highway flood is the product of natural disaster-causing factors(flood,rainstorm,human engineering activities,etc.),which is acting on the disaster-bearing body(highway,social economy,etc.)and is affected by the ability of flood prevention and disaster mitigation(disaster prevention and control,manpower and material resources investment,etc.)in a certain disaster-inducing environment.Aiming at the risk of highway flood disaster in the Chinese Mainland,this research makes an in-depth study on the risk zoning of highway flood disasters in the mainland of China through the analysis of its connotation,composition system impact factors and evaluation models,as well as the study on a large number of historical data,statistical data and field investigation.(1)By adopting the method of multi-attribute decision-making,hazard evaluation indexes for disaster-causing factors of highway flood were preliminary selected.Then,Level priority relationship method was used to establish the index system of hazard evaluation,including 5 disaster-causing factors,the average annual 24-hour maximum rainfall,flood return period,flood inundated area,flood inundated days and population density along highway.And the hazard area of disaster-causing factors was divided into5 levels: extremely high hazard area,high hazard area,medium hazard area,low hazard area and slight hazard area.Arc GIS was used to compile single-element thematic maps for each evaluation index.Based on entropy weight method and multiple correlation coefficient method,a synthetic weight method model was established.By coupling with TOPSIS method,a synthetic weight-TOPSIS hazard evaluation model was established to calculate the threshold value for each hazard area.According to the hazard partitioning method of highway flood disaster-causing factors,with the spatial superposition function and computing ability of Arc GIS,the hazard partitioning situation of disaster-causing factors in the Chinese Mainland was obtained.(2)Taking the fragility of disaster-inducing environment for highway flood as research object,the method of multi-attribute decision-making was used to build the index system of fragility evaluation,including 6 disaster-inducing environment indexes:terrain,land surface slope,geomorphic type,drainage density,geological disaster development along highway and vegetation cover.By using Arc GIS technology,single-element thematic maps for each evaluation index were compiled.AHP-expert coupling model was established to calculate each fragility index weight.Then on the basis of the comprehensive evaluation method,a model to evaluate fragility index was constructed.According to the calculated threshold value,fragility grading for each disaster-inducing environment index was determined.The regionalism of index grades was divided and the fragility zoning for disaster-inducing environment of highway flood in the mainland of China was obtained by using Arc GIS space superposition function and computing power.(3)For the disaster-bearing body of highway flood,by adopting the method of multi-attribute decision-making,the index system of vulnerability evaluation was obtained,which was including 4 disaster-bearing factors: highway grade,highway network density,highway property and per Capita GDP.In the meantime,Arc GIS technology was used to compile the single-element thematic maps for each evaluation index.The weight of each vulnerability evaluation index was determined by the method of the local index weight,then the grey clustering comprehensive analysis method was used to establish a vulnerability evaluation model for the disaster-bearing body of highway flood.With the support of Arc GIS system,vulnerability grades for the disaster-bearing body of highway flood were classified regionally.Thus,vulnerability areal distribution for the disaster-bearing body of highway flood in Chinese Mainland were obtained.(4)Based on features of highway flood disasters,according to the factor analysis method,4 typical representative indexes for the flood prevention and disaster mitigation of highway flood were selected,those were the density of hydrology and rainfall stations for a certain area,the investment for highway geological hazard prevention and control,forecast ability of geological disaster along highway and the proportion of labor force.Then,an evaluation index system for the validity of flood prevention and disaster mitigation was built and single-element thematic maps for each evaluation index were drawn by using Arc GIS technology.Those gained datum were dimensionless processed by using mean standardization method.According to the AHP-expert coupling model,each validity index weight for the flood prevention and disaster mitigation of highway flood was gained and then the validity comprehensive evaluation model was constructed.Subsequently,based on the Arc GIS software,calculated results were analyzed and validity grades zoning for the flood prevention and disaster mitigation of highway flood were gained.(5)Based on the existing research achievements,this study divided the risk evaluation of highway flood into 4 aspects: hazard of disaster-causing factors for highway flood,fragility of disaster-inducing environment for highway flood,vulnerability of disaster-bearing body for highway flood and validity of flood prevention and disaster mitigation for highway flood.Then the AHP-expert coupling model was selected to determine the weight for each risk index.And according to the principle of multi-factor composite index method,risk evaluation model for highway flood in the Chinese Mainland was constructed.Taking 2856 county-level administrative districts in the mainland of China as evaluation units and using1km×1km grid unit to build each evaluation index database,and the spatial analysis function of Arc GIS was used to calculate those datum.At the end,the risk grade distribution and the risk zoning of highway flood disasters for all county-level administrative districts in the mainland of China were obtained.