Spatio -temporal evolution characteristics of landslides in debris flow catchment in Beichuan County in the Wenchuan earthquake zone

The Wenchuan Earthquake on May 12, 2008 triggered a large -scale co -seismic landslide, and the subsequent heavy rainfall prompted the formation of a new landslide. These loose solid materials became the main material source for subsequent debris flow disasters, which seriously threaten people’s lives and property security. In order to explore the spatio -temporal evolution characteristics of the landslide in the debris flow catchment in the strong earthquake area, this paper takes the eight catchments dominated by the Weijiagou in Beichuan County as an example, and selects eight remote sensing images (after the earthquake in 2008, after the “9.24”debris flow, and in 2010, 2011, 2013, 2014, 2015 and 2016), to respectively interpret the landslides, and calculate their spatial distribution characteristics. We also calculated the vegetation coverage (VFC) and vegetation coverage recovery rate (VCRR) in the study area using the normalized vegetation index (NDVI). The research results show that the development area of the landslide in the study area reaches a peak after the heavy rainfall, and then it returns to a stable state, and the area decreases year by year. The collapse body has the largest development area in the range of 900-1 100 m in elevation, 30°-45° in slope, 90°-135° in the slope direction and 150 m in the channel. The vegetation coverage in the catchment was the lowest after the “9.24”debris flow disaster, and then recovered stably. In the period from the earthquake to 2010, the vegetation coverage recovery rate is more than moderate, and the vegetation restoration degree was low. After 2011, most areas in the catchments were at a medium or higher level of vegetation coverage recovery rate, and the degree of vegetation restoration was higher. By 2016, the vegetation coverage of the study area has returned to a high level of 0.86.This study also shows that vegetation has a certain inhibitory effect on debris flow activity.