基于斜坡单元鄂西山区典型集镇地质灾害风险评价

Risk Assessment of Geohazards Based on Slope Units in a Typical Mountainous County Town of Western Hubei Province

鄂西山区处于全省地质灾害高易发区,灾害频发,风险呈现加剧之势。以恩施州巴东县野三关集镇为研究区,通过以斜坡为单元地质灾害调(勘)查工作,归纳了孕灾地质条件,并构建了斜坡地质灾害风险评价体系:首先基于斜坡单元进行评价单元划分;然后采用层次分析法,选取斜坡坡度、斜坡高差、剖面曲率、工程地质岩组、地质构造、斜坡结构、水系密度、植被覆盖率等8个评价因子,对区内斜坡地质灾害易发性进行评价研究;综合考虑人类工程活动和降雨的诱发影响,进行不同降雨重现期工况下危险性区划;根据研究区人口、建筑、道路、土地等承灾体分布,分别进行人口和经济易损性评价;最后根据危险性和易损性评价结果,进行地质灾害风险评价,为野三关集镇发展规划、精细化“隐患点+风险区双控”体系建设提供了理论依据和实际指导。结果表明:随着降雨量的增加,高风险区和极高风险区的面积逐渐增加,主要集中分布在研究区东北片区,针对极高、高风险区地质灾害隐患点和有变形迹象的斜坡建议采取工程治理或专业监测措施,制定应急预案。

The mountain region of Western Hubei Province is a highly-susceptible area of geohazard,where landslides and rockfalls happen frequently.The study area is Yesanguan county town in the western of Hubei Province.Based on the detailed investigation of geohazard in slope units,the risk assessment model of geohazards was established after the distribution characteristics and related geological conditions of geohazards are analyzed.As the evaluation area was divided into slope units,slope unit,slope,slope height,slope curvature,slope structure,engineering geological units,geological structure,gully density,and vegetation coverage were selected as the evaluation indexes to construct geohazard susceptibility assessment model in the AHP(analytic hierarchy process).Combined with the maximum daily rainfall in different return period and human engineering activities,the assessment model of geohazard probability was proposed.According to the distribution characteristics of different types of hazard-affected bodies,a vulnerability model was set up.Based on geohazard probability and vulnerability assessment,the risk assessment is constructed,showing that the high risk areas lie mainly in the northeast of the study area and providing the scientific basis for urban construction planning and construction of“double-control of point and zone”system of geohazard risk management in the study area.