黄土区滑坡研究中地形因子的选取与适宜性分析

Suitability Analysis of Topographic Factors in Loess Landslide Research

黄土高原是中国生态较为脆弱的地区,也是滑坡发育的地层之一。黄土滑坡发育是孕灾环境、致灾因子和承灾体等多种因素联合作用的结果,其中作为重要孕灾环境因素的地形因子的选取是黄土滑坡风险研究的基础。本文选取黄土滑坡灾害多发的甘谷县作为研究区,综合利用敏感性指数、确定性系数和相关系数方法进行地形因子在滑坡灾害研究中的适宜性分析,得出以下结论:基于确定性系数法、敏感性分析模型和相关系数法,最终筛选出适宜于本区域滑坡灾害评价的地形因子为:坡度、坡度变率、坡形和地表粗糙度;确定性系数法、敏感性分析模型都基于分析单一因子与滑坡之间的关系进行致灾因子选取,忽视地形因子之间的相关性。实验结果表明,研究区稳定性较差的区域与已发生滑坡灾害分布数量具有较好的对应关系,并深入分析了滑坡与地形因子分级范围的关系,发现地形因子分级范围对地质灾害风险研究具有重要的影响,是导致部分区域的差异性主要原因之一。实地调查发现,河网切割密度及人类工程活动也对研究区危险性具有重要的控制作用,是重要的地形因素。

The region of loess plateau is one of the ecologically fragile areas in China. It is one of the slippery strata of which landslides often developed. The development of the loess landslides is the result of the combined effect of many factors such as the disaster environment, the disaster factor and the disaster bearing body. The selection of topographic factors which are important environmental elements of the disasters is the basis of the study of loess landslide risk. We take Gangu county as the study area, which is one of the frequent occurrence of loess landslide hazards in Gansu province. According to the basic conditions of landform, suitability analysis of topographic factors in the study area was carried out with models of sensitivity index （SI）, certainty factor （CF） and correlation coefficient （CC）. The following conclusions were obtained： Based on the models of SI, CF and CC, the topographic factors suitable for the loess landslide hazard research of this area are： slope, slope of slope （SS）, slope shape and surface roughness （SR）. The selection of disaster-inducing factors with the methods of SI and CF is merely based on the analysis of the relationship between the single factor and the landslides. We ignore the correlation between the topographic factors. The experimental results indicated that the area with poor stability in the study area has a good correspondence with the number of landslide hazard distributions. After deeply analyzing the relationship between the landslides and the grade range of the topographic factors, it is found that the grade range of the topographic factors has an important influence on the landslide risk assessment of the study area. This is one of the main reasons of the differences in some areas. Based on field investigation, the river-cutting depth, drainage density and human engineering activities are also important topographic factors and have key control effect on the landslides of this study area.