Risk Assessment Of Potential Debris Flow After Earthquake In Jiuzhaigou County,Aba Prefecture,Sichuan Province

Jiuzhaigou County is located on the anticline in the northern section of the Minshan Mountain Range in the western geosyncline of Sichuan Province.There are obvious fault zones on the north,south and west sides,which are complex and belong to the strong tectonic movement.In this area,the rock formation is strongly curved and broken,the structural fractures are developed.The “8·8” Jiuzhaigou earthquake induced a number of secondary geological disasters such as collapse and landslide,which led to the cracking of the mountain and the accumulation of loose solid matter.With the heavy rain,mudslides may occur at any time,seriously threatening local personal safety and economic development.Therefore,the use of new technologies and new methods to quickly identify the general distribution and traits of debris flow hazards in the disaster areas,and conduct risk assessments,not only provide a basis for disaster assessment,disaster mitigation and early warning and forecasting in the region,but also provides a reference for future Debris flow research.The risk assessment of potential debris flow is the basis and premise of debris flow prevention and early warning and forecasting in the disaster area,and the geological environment is destroyed after the earthquake,which reduces the starting conditions of debris flow.At present,there are few studies on the debris flow after the earthquake in Jiuzhaigou County,and The analytic hierarchy process is used to study the risk of regional debris flow,and the subjective factors are too large.In view of these problems,this paper takes Jiuzhaigou County as the research area and relies on the National Natural Science Foundation of China Youth Science Fund Project “Automatic Identification of Landslide Remote Sensing(41602355)under the Cognition of Surface Overlay Dual Topology Modeling”.Firstly,through field investigation,combined with existing data,the geological disaster interpretation and information extraction of the study area,to identify the spatial distribution characteristics of geological disasters.Secondly,the key impact factors are selected.The vegetation water content is introduced as the evaluation factor,and the factors are extracted by 3S technology.Then the subjective and objective factors are taken into consideration.The evaluation model makes a reasonable and scientific evaluation of the potential debris flow risk in the study area;finally,the field evaluation results are tested by field investigation.The main research contents and achievements of the thesis are as follows:(1)Using remote sensing images before and after the earthquake in the study area,through remote sensing image processing and geological hazard information extraction,the geological disasters in the study area were interpreted in detail,and 307 collapsed bodies,and 135 landslide bodies and 232 debris flow trenches were interpreted.Combined with topographic,geological and hydrometeorological data,the spatial distribution characteristics of geological hazards in the study area were identified.(2)The evaluation units of different scales are divided based on the basin;the formation conditions of debris flow in the study area are analyzed;the maximum rush volume,geomorphic information entropy,seismic intensity,geological structure,watershed area and main trench length of the debris flow are selected.10 risk factors such as relative height difference,slope,24-hour maximum rainfall and vegetation water content were used as evaluation indicators,and each evaluation factor was extracted by 3S technology.(3)The 12 debris flow disasters that occurred after the earthquake in the study area were selected as samples,and the weights of each evaluation factor were calculated by using the super-efficiency DEA-AHP model taking into account the subjective and objective factors.Through spatial statistical analysis,the factor values of each watershed unit at different scales are extracted,and the values are assigned according to the unified standard,thereby achieving risk zoning and evaluation.On this basis,the evaluation results are verified through field investigations.The results show that the results of this study are highly accurate and can better reflect the potential debris flow hazard in the study area.Among them,the mudslides in the Zhangzha Town and Jiuzhaigou Scenic Area and Luoyi Township are extremely dangerous,and it is urgent to pay attention.The research results provide a scientific basis for the early warning and prediction of potential debris flow hazards in the area.