Study On Flood Disaster Risk In Weihe River Basin

Flood disaster is a very serious meteorological disaster,which causes large losses to the social and economic development of our country,and it is also a major issue that our country faces now.The risk zoning is the basis of flood risk management,loss assessment is an important evidence of planning rescue programs,and flood risk zoning is also an important basis for government to prevent and reduce disasters.The study on the risk zoning of Weihe River Basin has great realistic and practical significance.Taking DEM elevation data,NDVI image data and three maximum precipitations from 2005 to 2015 of all precipitation sites of Weihe River Basin as an important data source of the risk assessment of Weihe River Basin,this paper determines the weight of impact factors of flood disasters through analytic hierarchy process and analyzes the flood risk of Weihe River Basin based on GIS spatial analysis.Then taking the total population,cultivated land area and GDP of Weihe River Basin as the data source of the flood disaster vulnerability,the paper determines the vulnerability of the flood disaster by analytic hierarchy process and draws flood distribution diagram of Weihe River Basin based on GIS spatial analysis.Finally,according to the research results of the risk and vulnerability of the Weihe River Basin,the risk assessment model of the Weihe River Basin is established.Through GIS spatial analysis and overlay analysis,the risk degree is confirmed and the flood distribution diagram is finished.On this research,the main conclusions are as follows:(1)The results of the flood risk assessment show that the middle and above flood areas of the Weihe River Basin are mainly distributed in the south of the Weihe River Basin including the south part of Xi'an,Baoji,Weinan and Tianshui,and the west flood zone including great part of Dingxi,Tianshui and Guyuan.Loess Plateau on its north and Qinling Mountain on its south occur less floods.The risk of flood disaster in western Weihe River Basin is higher than that in the eastern part.The proportion of the area with the lower risk is about 55.75%,then the area with moderate risk is about21.57%,next is the low risk area-about 19.33%.The proportion of the higher risk area is about 3.22% and the proportion of high-risk area is about 0.19%.(2)The results vulnerability assessment show that the flood vulnerability of WeiheRiver Basin has a strong spatial differentiation rule which shows a variation trend--higher in the southern area and lower in the western and eastern area.The maximum vulnerability area is Xianyang and Xi'an with an area of 11347.7 square kilometers and the proportion is 8.4%;the higher vulnerability area is Weinan,Pingliang,Baoji,Tianshu with an area of 22864.8 square kilometers and the proportion is 16.92%;the medium vulnerability area is Tongchuan,Guyuan and Dingxi with an area of 33444.5 square kilometers and the proportion is 24.76%;lower vulnerability area is Qingyang and Yulin with an area of 56029.8 square kilometers and the proportion is 41.48%;the lowest vulnerability areais Yan'an City with an area of11394.1 square kilometer and the proportion is 8.44%.(3)The Weihe River flood risk area is divided into five levels including higher risk zone,high risk zone,medium risk zone,low risk zone and lower risk zone.The higher risk zone is mainly distributed in the south and west of the basin,which is the south of Xi'an,the south of Weinan,the west and south of Dingxi,the west and east of Tianshui and the west of Dingxi with an area of 8608.1 square kilometers covering 6.37% of total basin;the high risk zone is mainly distributed in the northwest and central part of the basin,which is the north of Xianyang,the west and central part of Guyuan,the east and central part of Dingxi with an area of 26,316.9 square kilometers,covering 19.48%;the medium risk zone is mainly distributed in the middle and north of the basin which is the central part and south of Tianshui,Xianyang,the north,west and east of Qingyang,the east of Guyuan with an area of 42722.4 square kilometers covering31.63%;the low risk zone is mainly distributed in the southwest,middle and northeast of the basin which is the central part and north of Xi'an,Weinan,the northwest and southwest of Yan'an,the east of Pingliang with an area of 37396.7 square kilometers covering 27.68%;the lower risk zone is mainly distributed in the northeast and central part of the basin which is the southeast of Yan'an,the southeast of Baoji,the central part and sout of Qingyang with an area of 20037 square kilometers covering 14.83%.