Deformation monitoring and evaluation of unstable slope based on ground-based and spaceborne SAR images

Ground-based and spaceborne interferometric synthetic aperture radar (InSAR) were combined to monitor slope deformation and analyze the main influencing factors of an unstable slope on the right bank of the Dajinchuan River in Danba County, Sichuan Province, China. We applied the small baseline subset time series strategy with 656 ground-based radar scenes acquired in September 13 to 17, 2019, and 62 Sentinel-1 InSAR scenes from July, 2018, to October, 2020. The qualitative and quantitative deformation features of the unstable slope were studied, and the possible influencing factors contributing to slope instability, including the geological structure, topography, external environment, and human activities, were discussed. The area of maximum deformation detected by the ground-based radar is located in the bedrock above the target area with a maximum cumulative deformation of more than 30 mm during the observation period, whereas the maximum deformation rate detected by spaceborne InSAR exceeds 40 mm/year. The differences between these results were analyzed, and the reasons were discussed. We provide references and suggestions for investigating potential landslide risks by combining ground-based with spaceborne InSAR.