Research On Risk Assessment Of Landslide Geological Disaster In Xiluodu Reservoir Area

Because of its frequent occurrence,Landslide geological hazard has great threat to ecological environment and human society in the world.Due to the special geological environment and geological characteristics,geological disasters occur frequently in China.Among all types of geological disasters,The casualties and economic losses caused by landslide disasters rank first.Southwest China lies between the second step and the third step of the terrain ladder in China,The topography fluctuates greatly and the geological conditions are complex in this area,which provides sufficient background conditions for the development of landslides.With the continuous construction of large-scale water conservancy and hydropower projects in southwest China,frequent landslides have caused great losses to peopleundefineds lives,property and social economy in the reservoir area of hydropower stations.Because of the particularity of the reservoir bank landslide of the cascade hydropower station in southwest China,the risk assessment theory and method of the reservoir bank landslide of the cascade hydropower station in the southwest area is not mature at present.Therefore,this paper aims at this problem,based on the development mechanism of reservoir bank landslide,considering the intluence of reservoir water storage on landslide,the risk assessment and vulnerability assessment of reservoir bank landslide of Xiluodu Hydropower Station are carried out.Finally,the risk assessment of landslide is carried out.Local government departments can make corresponding disaster prevention and mitigation measures according to the results of risk zoning,which has a certain practical application value.Taking Xiluodu Reservoir area as the study area,169 landslides were determined by ground investigation and remote sensing image interpretation.On the basis of analyzing and studying the spatial distribution characteristics and disaster formation rules of landslides,the development mechanism of reservoir-bank landslides was set out from the point of view of the development mechanism of reservoir-bank landslides.According to Pearson correlation analysis and collinearity detection,the initial evaluation factors are selected to determine the final evaluation factors are elevation,height difference,slope,slope direction and lithology of stratum,according to the indexes which have little influence on landslide disaster and the factors with higher collinearity,which are selected from Pearson correlation analysis and collinearity detection.The average annual rainfall,NDVI and fluctuating zone are eight evaluation factors.The random forest model is used to determine the weight of each evaluation factor,Slope unit is selected as the basic evaluation unit.A landslide hazard assessment model based on slope unit is established in the study area.The evaluation results show that:There are 145 slope units in high-risk area and extremely high-risk area.accounting for 27.78%of the total number of slopes and 1166.67 km2 of the total area of the study area.32.07%,including 76.33%of the landslides in the study area,the distribution density of landslide hazard points gradually increases with the increase of risk degree.The relationship between them can be expressed by formula,and the correlation coefficient reaches 0.8569,which indicates that the evaluation results are reasonable.Analysis of Bearing Body Types Threatened by Landslide Disasters in Reservoir Area:Five vulnerability evaluation factors,namely population density,building density,road density,GDP density and cultivated land density,are selected from three aspects:population vulnerability,material vulnerability and economic vulnerability.The evaluation unit is kilometer grid,and the combination of analytic hierarchy process and variation coefficient method is used.The comprehensive vulnerability index model is used to evaluate the vulnerability of landslides in the study area based on grid unit.The evaluation results show that The evaluation results show that the area of extremely vulnerable and highly vulnerable areas of landslide hazards is 808 km2,accounting for 22.51%of the total area of the study area.These areas are mainly concentrated in Shanshubao,Nantian,Baitieba,Paha and Xiluodu near Xiluodu dam,and near the banks of the main stream of Jinsha River 10-30 km and 50-80 km away from the dam site,and Dashanbao,Paoma and Baihetan town at the end of the reservoir.By studying the theory of landslide risk assessment,the method of transforming grid unit vulnerability to slope unit vulnerability is established,and the spatial scale of risk assessment and vulnerability assessment unit is matched.The risk assessment model of risk=risk vulnerability is selected to evaluate the risk of slope unit and grid unit respectively.According to the statistical analysis of the evaluation results,the area above high risk of landslide based on slope unit and grid unit accounted for 32.51%and 37.1%of the total area of the study area,and the area below risk accounted for 67.49%and 62.9%of the total area of the study area,respectively.The two evaluation results showed that:landslide high-risk and above risk areas are mainly located in Shanshubao,Xiluodu,Xiluomi,Baitieba,Nantian and Wuguan Town,and Wuguan,Wuji,Shangtianba,Kahaluo,Huanghua and Daxing Town on the right bank of Jinsha River about 20-40km away from dam.The closer it is to Jinsha River,the probability of high landslide risk grade is greater.Most of the low risk areas are located at the edge of the study area far away from Jinsha River,and the landslide risk grade in most areas of the first part of the reservoir is higher than that in the area at the end of the reservoir.