Risk Assessment Of Geological Hazard In Yangchun City Based On GIS

Yangchun city is located in the middle section of Wuchuan-Sihui fault zone,and the local fault structure is strongly developed,forming a structural system pattern dominated by northeast structure and supplemented by north-south and east-west structure.The engineering geological rock group is mainly layered soft metamorphic rock group.Due to its unique tectonic position,the terrain of the study area is undulating and mostly dominated by high mountains and hills.Factors such as obvious structural fragmentation,wide distribution of soluble rocks,and strong human engineering activities have led to frequent geological disasters.At the same time,Yangchun city has a high degree of geological disaster development,a wide range of distribution and a high degree of field identification,which is a good area for geological disaster risk assessment.Based on the collection of stratigraphic,tectonic and rock data in the study area,the types,development degree and distribution characteristics of geological hazards in Yangchun were identified through field geological survey and combined with remote sensing interpretation.The main types of geological hazards include 12 landslides,24 landslides,5mudslides,19 ground collapses,and 1031 geological condition points,mainly concentrated in the western mountainous areas.Based on the weights,the evaluation factors of the study area can be divided into 11 influencing factors,such as elevation,slope,slope direction,slope morphology,geomorphology type,distance from fault,engineering geological rock group,distance from water system,normalized vegetation index,road distance and land use type.Based on the information model,the information-AHP model and the deterministic coefficient logistic regression model,the susceptibility of the study area was evaluated.The ROC curve was used to verify the accuracy of the model.The results showed that the information-AHP method had the highest accuracy(AUC = 0.950).The results showed that the proportion of low,medium,high and very high susceptibility areas was 62.2 %,20.7 %,12.6 % and 4.5 %,respectively.Combining the results of susceptibility assessment with the average annual rainfall(2009 ～ 2020),the risk assessment of the study area was carried out by using the analytic hierarchy process.The results showed that the proportion of low,medium,high and very high risk areas in Yangchun city was 53.62 %,31.36 %,13.16 % and1.86 %,respectively.The six index data of population,construction,cultivated land,industrial and mining land area,highway and pipeline density in Yangchun city were collected,and the fuzzy comprehensive evaluation method was used to evaluate the vulnerability of geological disasters in Yangchun city.The results show that the medium and high vulnerable areas account for 24.64 %,and the medium and high vulnerable areas are mainly concentrated in the middle of Yangchun city.Based on the risk assessment and vulnerability assessment,the risk assessment of geological disasters in Yangchun city is obtained by matrix analysis of the two results through Arc GIS.The results showed that the proportions of low,medium,high and very high risk areas were 57.16 %,34.18 %,6.5 % and 2.16 %,respectively.