STATISTICS OF CHARACTERISTIC PARAMETERS AND EVOLUTIONARY MECHANISM OF LANDSLIDES IN TYPICAL AREA OF LONGZHONG LOESS PLATEAU: A CASE STUDY OF TIANSHUI CITY
Tianshui City (34°5'5"~34°49'40"N,105°13'15" ~ 106°42'58"E) is one of the mountainous cities of Longzhong Loess Plateau which are threatened by the landslides seriously. Loess landslides spread widely and have seriously restricted the urban construction and economic and social development. In this research,a detailed and reliable database about the landslide spatial distribution was established. It was based on the analysis of the historical resources and the remote sensing data, and on the field investigation. As a result, 470 landslide hazard data samples are acquired. The scale of the landslide samples is the typical medium-sized loess landslides with over 1*10~4m~2 in area and over 100m in length. According to the DEM data of SRTM with the resolution of 30m, GIS spatial analysis modules, and the landslide database, six characteristic parameter index of loess landslides are obtained,including the average altitude, relative height, average slope,landslide area,landslide length and sliding direction. The research results show that the medium-sized loess landslides in Tianshui City are mainly with the following features: the average altitude is between 1200 ~1400m, the relative height is between 50 ~ 150m, the average slope is between 10° ~15°, the landslide area is between 1 * 10~4 ~10*10~4m~2,the landslide length is between 200 ~ 600m, and the main sliding direction is southwest and west and northwest and north and northeast. The landslides are characterized by low elevation, small height difference and gentle angle. The surface morphology of the landslide is relatively even and the slope erosion is relatively weak. Based on the aforementioned analysis, the mechanism of regional landslides evolution in Tianshui City was discussed,and the mechanism models of landslides development and evolution was established. From the aspect of development and evolution, those landslides in research area are mainly controlled by tectonic movement and climate change. The wide-spread regional landslides in Tianshui City are the exact feedback of the complicated geological condition and the climate shifts. In specific area, the regional geological features and climate environment play a decisive role in the development of landslides.