基于长时间尺度下滑坡易发性评价研究———以甘肃省永靖县为例

利用决策树模型,基于五期土地利用评价因子,对甘肃省永靖县进行近40年的长时间尺度下的滑坡易发性评价,五期评价结果均显示研究区内滑坡灾害的极高和高易发性区域主要集中在中部黄河流域(盐锅峡镇至刘家峡水电站段)周边、西南部川城村—红泉镇—王台乡周边区域以及中部偏东的三条岘乡,该区域人口密集,人类活动较多.研究结果与前人研究结果类似,且通过受试者工作特征曲线的精度检验,说明五期评价结果均具有较高的可靠性.另外,研究区内的自然植被和裸土地与滑坡易发性指标之间具有负相关关系,而旱地、水域和城乡建设用地等人类活动频繁的区域则更容易导致滑坡灾害的发生.从时间尺度上来看,极高和高易发性分区面积逐年下降,但自 2000年,极高和高易发性分区面积减少速度出现显著减缓,同期,该区域内的土地利用变化为城乡建设用地面积增加而植被面积减少,这使得区域内边坡稳定性下降,使部分防灾工程措施的减灾能力下降.本研究为该地区的灾害预防、预测和城乡土地规划提供了参考.

Landslide susceptibility assessment based on long time scale: a case study of Yongjing County, Gansu Province

The decision tree model was used in this study to assess the landslide susceptibility in Yongjing County over a long time scale of nearly 40 years based on land use over five periods. Evaluation results show that the extremely high and high susceptibility zones of landslide disasters are mainly concentrated around the Yellow River basin (from Yanguoxia Town to Liujiaxia Hy ^-dropower Station) in the middle of the study area, the adjacent areas around Chuancheng Village-Hongquan Town-Wangtai Township in the southwest of the study area, and Santiaoxian Township in the middle east of the study area. The region is densely populated with many human activities. The results of this study are similar to those of previous studies, and the accuracy test with the receiver operating characteristic curve shows that the evaluation results of the five phases are highly reliable. In addition, a negative correlation is observed between the natural vegetation and bare land in the study area and the landslide susceptibility index, while the areas with frequent human activities, such as dry cropland, river area, and urban and rural construction lands, are likely to cause landslide disasters. From the perspective of time, the area of the extremely high and high susceptibility zones decreased yearly, but the reduction rate of the area has significantly slowed down since 2000. The area of urban and rural construction land in the region increased, and that of vegetation decreased during the same period. Hence, the stability of slopes in the region was reduced, and the capability of some disaster prevention measures was weakened. This study provides a reference for disaster prevention and subsequent urban and rural land planning in this area.