Risk Assessment Of Debris Flow In Dongchuan County,Yunnan Province

Debris flow is a worldwide disaster that is extremely sudden and destructive.The geological disaster risk assessment can fully evaluate the relationship between disasters and humans.It can provide important basis for debris flow disaster prevention and mitigation and urban construction planning.The special natural conditions and geological environment conditions in Dongchuan County of Yunnan Province determine the inevitability of debris flow disasters.In this study,Dongchuan county was selected as the research object,aiming to analyze the risk of debris flow in the study area,establishing an evaluation system that combines geographic information systems and remote sensing technologies.The conditional probability model and the analytic hierarchy process are applied to the qualitative and quantitative assessment of the debris flow in Dongchuan County.The hazard-subsequent bodies are classified by the object-oriented classification method to determine the vulnerability of the debris flow.Its main research content is as follows:(1)Research Based on GIS technology,Analysising debris flow hazard assessment by selecting six evaluation factors in this study,including elevation,slope,stratum lithology,distance from fault interface,land use,and normalized difference vegetation index.we proposes that use conditional probability models to quantify the evaluation factors,then use the analytic hierarchy process to calculate the weight of each evaluation factor,establishes a multi-factor evaluation model,and calculates the potential hazard of debris flow.Dividing the risk of mudslides in the study area into:medium hazard area,low hazard area,very low area,high hazard area,and very high hazard area.The results show that the areas with high and extremely highly dangerous are mainly distributed in the valley of Jinsha River,Xiaojiang River,Kuai River,Wulong River,respectively accounting for 41.2%and 17.5%of the study area.The verification results that based on field survey data show that:The results of the evaluation are in accordance with the actual situation.(2)In order to achieve the vulnerability assessment of debris flow in Dongchuan County,this study combined the current land use status of Dongchuan County and set the disaster-affected body as:cultivated land,forest land,construction land,and traffic land,analysising the characteristics of the disaster-bearing body.Based on the object-oriented classification method,features including spectrum,shape and texture are selected to establish classification rules and extract hazard-bearing bodies.The results show that the object-oriented classification method achieves an accuracy of over 84%in the extraction of hazard bearing bodies.According to the investigation,the actual value of each disaster-bearing body was obtained,and normalized treatment was conducted to obtain the vulnerability zone of debris flow in Dongchuan County.(3)The risk assessment of debris flow disasters is based on the calculation results of danger and vulnerability,and obtain the risk value from the product of risk and vulnerability,Reclassify the risk and divide debris flow risk into five levels according to natural break method The results show that the area with high risk above is about 208.66km~2,accounting for 11.4%of the area of Dongchuan,mainly distributed in the urban areas of Dongchuan County and the construction land which distribute along the valley.