Identifying the Mechanism of Toppling Deformation by InSAR : A Case Study in Xiluodu Reservoir, Jinsha River

The impoundment of reservoirs in canyons can aggravate the destruction of bank slopes. The Xingguang village landslide is located on the Xiluodu Reservoir in the lower reaches of the Jinsha River. It has deformed continuously since impoundment of the reservoir in 2012, and it seriously threatens the operational safety of the Xiluodu hydropower station. Its temporal and spatial deformation characteristics and its deformation mechanism have not been systematically monitored and explained. In this paper, the movement directions were identified based on the time-series cumulative displacement maps and the landslide is further partitioned into different sections by combining geomorphological data, stratigraphic occurrence, and lithological characteristics. The horizontal and vertical displacement characteristics of the two sections of the Xingguang village landslide were obtained by ascending and descending track interferometric synthetic aperture radar (InSAR) observation results and two-dimensional decomposition functions, and the results were further verified by a field survey and unmanned aerial vehicle (UAV) photography. The results show that the lithologic combination of alternating soft and hard anticline strata and the high steep bank slope cut by the Jinsha River are the internal factors responsible for the development of the Xingguang village landslide. The softening of the strata caused by water storage and the pressure difference caused by water level fluctuations reduce the slope stability. This study provides a new technical path to obtain the direction of landslide movement through time-series cumulative displacement maps and stratigraphic information and then identifies rock toppling in a remote way, which is of great significance for the prevention and control of rocky slope failures in canyon reservoir areas.