Risk Assessment Of Mountain Flood Disaster In Sanchuanhe Basin

China is a mountainous country,and mountain flood disaster caused by heavy rainfall continue to occur.The mountain flood disasters have destroyed industrial and agricultural production conditions and threatened the safety of people's lives and property,and hinders social and economic development to a certain extent.At present,there are still many weak links in risk assessment and prevention of mountain flood disaster in China's disaster prevention and reduction system.Sanchuanhe is a tributary of the left bank of the Yellow River in the loess hilly and gully region of western Shanxi,the basin is located in the west of the Lv-liang mountains,with an area of 4161km2.The height difference of the region is large,gully beam and ridge are continuous,the density of gully and the ratio of vertical slope are relatively large;The spatial and temporal distribution of rainfall is very different in this area.It has the characteristics of high intensity and short duration,and this land is a frequent occurrence area of mountain flood disaster.At the same time,the area is also a concentrated area of industry,agriculture and population in Lvliang,Shanxi province.Human activities in this area are frequent and it belong to the economic growth belt of Lvliang.Therefore,the investigation and analysis of the flood disaster in this basin and the evaluation of its risk from the multidimensional degree can not only provide the basis for the local disaster prevention and reduction,but also have certain practical significance for the local social stability and the sustainable development of the economy.In this paper,the Sanchuanhe Basin is selected as the risk assessment object of mountain flood disaster.Based on the analysis of domestic and foreign research results,combined with mountain flood disaster system theory to construct the risk assessment system of mountain flood disaster,consisted of target layer,comprehensive layer,standard layer and evaluation index layer.Based on the principles of comprehensiveness,representativeness and operability,the rainfall intensity,the rainfall above rainstorm,the surface elevation,the stratigraphy and lithology,the land use type,the river network density,the topographic slope,the topographic wetness index,the and frequency of historical mountain flood disasters are selected from three aspects of the disaster factor,the disaster environment and the historical mountain flood disaster to used as evaluation indexes of natural environmental vulnerability of mountain flood disasters;the non-engineering measures of mountain flood disaster prevention distribution density,the reservoir capacity density,the embankment distribution density,the buffer area,the population distribution density,the proportion of cultivated land,and the enterprises distribution density are selected from two aspects of the current mountain flood disaster prevention capacity and potential loss value to used as evaluation indexes of social environmental vulnerability of mountain flood disasters.According to related regulations and previous research results,the indicators are graded,and used ArcGIS software to draw evaluation index classification thematic map.Using the AHP,entropy weight method and game theory to calculate the subjective weight,objective weight and comprehensive weight of each index,and the index superposition method is used to calculate the natural environment vulnerability index and the social environmental vulnerability index of mountain flood disasters,and then the risk zoning of mountain flood disaster in Sanchuanhe Basin is defined.The research area is divided into four different risk zones,including high risk area,higher risk area,lower risk area and low risk area,it accounted for 15.71%,31.46%,35.69% and 17.14% of the total basin area,respectively.