Risk Assessment And Division Of Geological Disasters Based On GIS

Derong county is located in Ganzi Prefecture in the southwest of Sichuan Province.It is the northernmost section of the South-North structural system of Sichuan and Yunnan in the middle of the Sini type structural system of Qinghai Tibet.The complex structure in the area,together with the influence of frequent earthquakes,short-term heavy rainfall and human damage to the geological environment,makes the fragile geological environment more sensitive,and induces a large number of debris flows and landslides And geological disasters mainly caused by collapse.In view of this situation,this paper takes 303 geological disasters in Derong County as the research object,combines remote sensing data interpretation and field investigation,and uses DEM of Derong County Based on ArcGIS platform Data and remote sensing image extract slope,slope direction,elevation and other disaster factors,combined with the disaster factor layer and historical disaster data to find out the induced factors,development characteristics and distribution rules of geological disasters in the study area.During the risk assessment,nine secondary disaster causing factors are selected,which are topography factors(elevation,slope,topographic relief,slope type structure),geological structure factors(fracture structure,engineering geological rock group),meteorological and hydrological factors(river system,annual rainfall),human engineering activity factors(distance between disaster point and road).Then select the information quantity model,AHP information quantity coupling model and logistic information quantity coupling model to evaluate the geological disaster risk in the study area,and finally compare the AUC value of the three models with ROC curve.From the results,it is obvious that the accuracy of the coupling model is better than that of the single information model,and the logistic information coupling model is better than the AHP information coupling model.Therefore,according to the results of logistic information coupling model,Derong county is divided into five risk areas:high,high,medium,low and low.The vulnerability factors of population,cultivated land and road density are selected for vulnerability assessment of the study area,and the vulnerability assessment of towns in Derong county is carried out quantitatively by using the fuzzy comprehensive evaluation method,and the vulnerability assessment grades of each town are divided.Among them,there are 4 towns with high vulnerability,2 towns with medium vulnerability and 6 towns with low vulnerability,accounting for 18.8%,16.8%and 64.4%of the total area of the county respectively.Through the superposition operation of risk and vulnerability assessment results by using ArcGIS analysis function in Derong County,the high-risk areas are found to be mainly distributed in baisong,Ciwu,Chengguan,Gongbo,Zigeng,Xulong and szzha along the Dingqu river The area of the belt is mainly distributed around the township and along both sides of the Dingqu River,with a disaster point density of 0.861/km~2,which is composed of7 sub regions;the medium risk area is mainly distributed in the area of the Mayi River Basin,the xuqu River Basin,the Jinsha River coast,and the area of muzegong kasegon,with a disaster point density of 0.106/km~2,which is composed of 8 sub regions;most of the low risk areas are original forest areas and pastures The disaster point density is 0.033/km~2.