Development Characteristics And Hazard Assessment Of Debris Flows Along The Ranwu-Bomi Section Of Sichuan-Tibet Highway

A large number of glaciers and glacier-lakes are developed in the area along Ranwu-Bomi section of Sichuan-Tibet Highway, the causations of debris flow occurrence in this area are different from the typical rainstorm debris flow.Hazard assessment of debris flows is selected as object of study in this paper, in order to provide a basis for the local hazard prevention and mitigation, at the same time, build a suitable model for the area where include some plateau glaciers to enrich theoretical study of debris flow hazard assessment. Based on field surveys and lab analysis, found that in the study area, debris flows show a certain degree of distribution rules and development characteristics. Analysed the causations of debris flow occurrence from three respects that is terrain condition,material and water sources, results show the three respects are very beneficial to debris flow occurrence, they produce debris flows widely distributed in the study area. Based on above analysis, preliminarily selected assessment factors, which include: slope, elevation, the distances to faults, lithology, seismic peak ground acceleration, annual precipitation, annual mean temperature, glacier distribution density, glacier-lake distribution density. Analysed data correlation between every two factors, results show both annual mean temperature with elevation and annual mean temperature with annual precipitation have strong correlation, so eliminated annual mean temperature and retained others to reduce the repeated contribution of debris flow hazard that assessment factors make. Researched the relationship between each index factor and debris flow occurrence, research shows that lithology, seismic peak ground acceleration, annual precipitation,glacier distribution density, glacier-lake distribution density are positive indexes,elevation, the distances to faults are negative indexes, slope is interval index.Built debris flow hazard assessment index system combined with the information entropy method and GIS technique to evaluate and compart the debris flow hazards, the study area was divided into four regions according to different hazard levels: low, medium, high, very high. Results show that low, medium,high, very high hazardous areas account for 18.30%, 26.37%, 39.30%, 16.03% of the whole study area, respectively.