基于地貌演化的黄土滑坡敏感性分析

Sensitivity of loess landslides based on geomorphic evolution theory

甘肃天水麦积区位于陇西黄土高原,受强降雨和历史地震的影响,地表沟壑纵横,滑坡分布广泛。如何判断不同成因滑坡的敏感性与地貌演化阶段的对应关系是值得深入研究的问题。通过详细的野外调查,总结滑坡的形态特征,将区内滑坡分为降雨诱发型和地震诱发型。基于地貌演化理论,利用面积-高程曲线参数HI值和K值判断各小流域发育阶段与侵蚀程度,开展研究区滑坡敏感性分区。结合野外实地调查获得的滑坡分布数据,计算各个不同敏感区的地震滑坡和降雨滑坡面积比例,探讨不同成因形成的滑坡的分布趋势与地貌演化阶段的对应关系,并对敏感性分区结果进行验证。分析结果表明:高敏感区(壮年期)HI值为0.35～0.6,占全区总面积的67.87%;中敏感区(幼年期)HI值为0.6～1,占全区总面积的21.33%;低敏感(老年期)区HI值为0～0.35,占全区总面积的10.8%。K值与HI值整体呈正相关关系。各敏感性分区内地震与降雨滑坡的面积与分区面积的比值随敏感性的增加而增加,降雨滑坡在中敏感(幼年期)区中分布比例最高,多为黄土浅表层滑坡,地震诱发滑坡在高敏感区(壮年期)中分布比例最高。

Maiji District of the Tianshui city in Gansu Province is located in the Longxi Loess Plateau,northwest China.,The landslides are widely distributed on broken ground due to heavy rainfall and historical earthquakes.How to estimate the relationship between the sensitivity of landslides with different causes and the geomorphic evolution stage of ground is of great interests.This paper summarized the morphological features of landslides through detailed field investigation,and divided them into rainfall induced or earthquake induced.The parameters HI and K in the area-altitude curve of the geomorphologic evolution theory were calculated to assess evolution stages and erosion extent of each catchments.Regional landslide susceptibility zoning was mapped.Combining with actual landslide distribution data,the ratio of seismic landslide and rainfall landslide in each sensitive zone were estimated.Furthermore,the correspondence between landslide distribution with different causes and geomorphologic evolution stage was discussed to verify the sensitivity zoning.Three conclusions were drawn:1)The high sensitivity partition with parameters of HI 0.35 to 0.6 accounted for 67.87% of the region;The moderate sensitivity partition with HI from0.6 to 1 accounted for 21.33% of the region;and the low sensitivity partition with HI from 0 to 0.35 accounted for 10.8% of the region.2)The parameters HI and K were positively correlated.3)The ratio of the two type landslides areas to their sensitive area increased with sensitivity.The rainfall landslide mainly occurred in the moderate sensitivity partition and showed shallow landslide.The seismic landslide mainly occurred in the high sensitivity partition.