| Qingchuan County,located in the northern part of Sichuan,has complex geological formations and obvious topographic cuts.With the rapid modernization,human engineering activities have become more frequent,and the repeated occurrence of extreme weather such as heavy and continuous rainfall has bred large and small geological hazards,threatening the safety of local people’s lives and properties.For the sake of the harmonious development of local human society and natural environment,it is of great significance to conduct a study on the risk evaluation of geological hazards in Qingchuan County.This paper takes geological hazards in Qingchuan County as the research object,and uses cluster analysis,deterministic coefficient method,logistic regression model,and hierarchical analysis to evaluate the vulnerability,hazard,and fragility of geological hazards in the study area,and based on the theory of geological hazard risk evaluation,the following conclusions are drawn:(1)Qingchuan County has 117 geological hazards and potential hazards,including 107 landslides,8 cave-ins and 2 mudslides,with no particularly large number of hazards in each township.The geological disasters are mainly small and medium-sized,accounting for97.43% of the total number of disasters.The hazards are concentrated in the vicinity of water systems,mostly occurring during the peak of summer rainfall,and mainly distributed in the loose rock type areas in terms of stratigraphic lithology.The two mudslides in the study area,one has stopped developing and one is developing trend.(2)The density of disaster sites was selected as the historical factor based on the distribution pattern of geological hazards in the study area and the breeding conditions;the distance from water system,distance from roads,lithology of strata,slope,slope direction,elevation,distance from faults and vegetation coverage were selected as the evaluation factors of vulnerability of the study area.The 20-year average rainfall was used as the time influence factor,which together formed the geological hazard evaluation index system of Qingchuan County.The K-mean analysis method and CF+LR coupling model were used to evaluate the susceptibility respectively.The two types of susceptibility evaluation and rainfall superposition analysis were used for hazard evaluation,and four hazard zones,such as very low hazard zone,low hazard zone,medium hazard zone and high hazard zone,were obtained.(3)Considering economic infrastructure construction and environmental ecological balance,etc.,population density is selected as population vulnerability,road density and GDP density as material vulnerability,and arable land density as environmental ecological vulnerability.These four factors together constitute the evaluation system of geological disaster vulnerability in Qingchuan County.The vulnerability evaluation by cluster analysis method and vulnerability evaluation by hierarchical analysis method were carried out by SPSS software,and four regions of very low,low,medium and high vulnerability were obtained.(4)Through ROC test,it can be known that the coupled model of CF+LR with hierarchical analysis overlay has high accuracy,so this is chosen as the final geological hazard risk evaluation model.The final geological hazard risk evaluation zoning map of Qingchuan County is obtained,which is four areas of very low,low,medium and high risk.Among them,the area of very low risk zone is 1240.36 km~2,the area of low-risk zone is743.75 km~2,the area of medium risk zone is 916.21 km~2 and the area of high risk zone is312.17 km~2.The density of hazard points increases with the increase of risk level in each subzone,which is consistent with the actual situation. |
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