Analysis of deformation characteristics for a reservoir landslide before and after impoundment by multiple D-InSAR observations at Jinshajiang River, China

The stability of reservoir bank slopes is always of great concern in hydropower construction. After impounding, some unstable slopes may fail, leading to landslides with significant displacements. This work investigated the vertical and horizontal displacements of the Yizicun landslide before and after impoundment of the Xiluodu Reservoir on the Jinshajiang River, southwestern China using InSAR technique and data from ALOS PAL-SAR, ENVISAT-ASAR, TerraSAR-X and Sentinel-1. The purpose was to explore the relationships between the ground surface deformation and the landslide movement mode, and to make further analysis on its deformation characteristics. Combining with field investigations, the analysis of InSAR reveals that the Yizicun landslide was a push type before impoundment and is a pull type after impoundment. This landslide is largely a whole slump with multiple slip surfaces. After the impoundment of the reservoir, the landslide boundary had a tendency to spread, and its rear edge has extended backward about 20 m. More fissures and secondary landslides appeared on the southern boundary than those in the north. The horizontal movement changed from southwestward to westward, and the vertical deformation increased. The current stability of the landslide might be subjected to a combined action of ground water levels and precipitation intensity. The study also indicates that InSAR has many inimitable advantages in the study of reservoir landslides, such as backtracking for stability of bank slopes before impounding, three-dimensional monitoring of active areas, landslide movement mode analysis and so on. Thus, it is a suitable method to efficiently analyze landslide deformation characteristics before and after reservoir impoundment, which is of great significant for detecting and monitoring reservoir landslides.