Sensitivity of loess landslides based on geomorphic evolution theory

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 from 0.6 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.

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