Assessment Of Debris Flow Hazard In Xunhua County

As a sudden mountain hazards,debris flow still has been short of accurate and effective forecasting methods.Mitigation Engineering only works for a certain scale disasters as a role of defense.In this case,how to determine the scope of the risk of debris flow,divided into danger area of different degrees,how to apply it to debris flow mitigation practice that make all types of human construction avoid debris flow hazard area,and avoid the disaster get worse,has become particularly important and urgent.Debris Flow Hazard Assessment is an important content of pre-disaster assessment of debris flow,also as an important part of disaster prevention and mitigation system.It has important practical meaning to reduce the direct and indirect losses of debris flows and develop evacuation and emergency rescue measures.It changes negative rescue to proactive prevention.Xunhua County is one of the most fragile ecological regions of China,which located in the transition zone between the west of the Loess Plateau and the Tibetan Plateau-Special natural and geographical environment and the geological environment conditions lead to the unique environment geology problems in this region.Debris flow is one of the main geological disasters in the survey area.The disaster not only caused serious losses to the local people’s lives and property,but also seriously restrict the development of local economy.Based on field investigation and extensive data collection,this paper studied the distribution and formation mechanism of Xunhua Debris Flow.Considering the geo-hazard distribution,geological environment and evoked factor,the paper selects 9 factors as assessment factor system including the existing hazard point,slope angle,Gully density,penetration depth,engineering geological rock group,the distance to fault,NDVI(Normalized Difference Vegetation Index),the rainfall and human engineering activities.Gully density and penetration depth which extracted from watershed unit is closely related to the gradient of debris Flow Gully and surface runoff.As the more important geomorphological indicators,make the evaluation results more targeted.The Analysis Hierarchy Process(AHP)method is applied to build the evaluation system of debris flow.With the help of ArcGIS Spatial analysis function,a 32x32 meter grid is used as the basic evaluation unit to achieve the assessment of the study area of debris flow hazard.According to the Xunhua debris flow hazard zoning map,the county is divided into four grades.The high-risk area of debris flow is mainly distributed in the north-central region of the Yellow River basin,JieZi River and Qingshui Basin,accounting for 14%of the county area.This area has complex landform conditions,the population density is relatively large,Considering the highway,water conservancy and hydropower facilities,urban buildings and temples and other important engineering facilities,this area needs to be monitored closely.This thesis has studied the Hazard Assessment of Xunhua Debris Flow.By determining the hazard rank of debris flows in different regions,improve vigilance to the residents lived in high-risk areas.It can provide the basis and reference for Regionalization of Debris Flow Danger Degree in other counties along the Yellow River in Qinghai.The research results is conducive to enrich and improve the theory and debris flow hazard assessment research methods to a certain extent.