密云水库周边山区滑坡泥石流易发区预估

Occurrence Probability Estimation of Landslides and Debris Flows in Mountainous Areas Surrounding the Miyun Reservoir

滑坡、泥石流等地质灾害的易发度主要是地质灾害自然属性特征的体现,它与孕灾环境的各项因子密切相关。这些因子包括地形地貌、流域水文、构造等内部条件因子以及地震、降雨等外部触发因子。为突出反映滑坡及泥石流主导因子的作用,本文参考了许多研究所采用的评价方法和因子选择,重点选取对该地区滑坡及泥石流发生区域分析评价起一定主导作用的、便于研究区域数据资料与空间资料匹配、关系密切的几个指标,包括地形地貌要素(坡度、坡向、坡形、相对高差、地貌类型)、环境要素(植被指数、河网密度、洪水淹没范围)、构造要素(距断层的距离、断层密度、地质岩性),通过对这些因子的敏感性进行分析,采用专家打分方法确定每种要素及因子的权重,借助因子加权叠加办法得出研究区地质灾害易发程度空间分布,用于表示其可能发生的统计意义上的可能性(概率),该研究对于区域地质灾害预防具有一定的适用价值。

The occurrence of landslides and debris flows is a type of the natural geological disasters, and is closely related to many factors of hazard-formative environments. These factors include both internal conditional factors such as landform and hydrologic and tectonic conditions, and external conditional factors such as earthquakes and rainfall. To highlight the factors that have dominant role to cause debris flows and landslides, referring to the evaluation methods and factors selection in many investigations, this paper presents the regional anal- yses and evaluations on the factors which have determinative effects on the occurrence of landslides and debris flows based on regional spatial data. A weighting method is built based on experts＇ experience for all indicators to estimate the occurrence probability of landslides and debris flows. These indicators include landform factors （slope, aspect and slope-shape, relative height difference, and geomorphologic types）, environmental factors （vegetation index, channel density and flood submerged area）, and geological structural factors （fault distance and density and geological lithology）. Based on the sensitivity analysis of these factors, the risk degrees of geo- logical disasters can be obtained by means of multi-factor superposition, which represent the possibility of geo- logical disaster on the statistical meaning （probability）. The study is helpful to regional geological disaster pre- vention. In comparison with the location of the field-surveyed disaster sites with the forecasted disaster zones, it can be concluded that there is a good accordance between the distribution areas of landslide and debris flows and the estimated disaster zones. The geological hazards such as landslides and debris flows are mainly distributed in the 10 km buffer zone of faults, and most of them occur in the zones with the heights of 500-800 m and the slopes of 5°-25°.