Reconstructing the Evolution of Slow-Moving Landslides in Steep Canyons using multi-platform satellite images

As an important part of geomorphic unit in high mountain area, Steep Canyon is one of the areas where slow-moving Landslide occur most frequently and with the largest scale due to its complex geological setting, steep terrain and intense river erosion, which pose serious risks to infrastructure and people downstream. We focus here on the slow-moving landslides along Jinshajiang steep canyon in the Southeast Tibet of China to revel the scientific issues what factor control the evolution process of these landslide. We estimate the ground displacement from time series analysis of Landsat series images and Sentinel-1 SAR images, spanning a more than 10 year period. Then field surveys on typical landslides were carried out, including reconstructing their three-dimensional structure, obtaining their material composition and rock mass structure and crevices information. The results show that there are significant differences in the deformation velocity of slow-moving landslides in the steep canyon. Specifically, the fastest landslide deformation velocity reaches 67 meters per year, so that this change can only be reversed by the correlation analysis on optical image. On the contrary , the slowest landslide deformation velocity is less than 1 meter per year, and this deformation can usually only be retrieved by time-series SAR technology. Combined with the field investigation and data analysis of meteorological stations and hydrological stations, we found an interesting phenomenon that the factors affecting the accelerated deformation of landslides are determined by the material and structure of the landslide. Accelerated deformation of high-level bedrock landslide have an obvious response to rainfall infiltration damage, but accelerated  deformation response of loose accumulation landslide and ancient landslide is resulted from to river peak discharge. These observations provide a basis for us to build a regional landslide dynamic prediction model in steep canyon that pave the way of dynamic risk management of slow-moving landslide.