Surface displacement and topographic change analysis of the Changhe landslide on September 14, 2019, China

Abstract

On September 14, 2019, a reactivated landslide with a volume of 1.3 × 107 m3 occurred in Changhe Town, Tongwei County, Gansu Province, China. As a result, a provincial highway, brickfield, and bridge were destroyed. Based on field investigation, interferometric synthetic aperture radar (InSAR) as well as unmanned aerial vehicle (UAV) photogrammetry, high-resolution remote sensing imagery, and digital elevation model, we addressed the surface displacement, travel distance, topographic changes, and causative factors of the Changhe landslide. The result shows the combination of ascending and descending orbit datasets can not only be used to monitor the landslide surface displacement but also to verify the deformation results. This landslide is a typical retrogressive landslide where large pre-failure deformation exists in the lower part of the landslide body. We detected the surface travel distance of the landslide and found spatial differences exist in the surface travel distance of the landslide. The deposit volume slightly exceeds erosion volume due to decompaction during the landslide. The frequency distribution of the basic topographic factors before and after the landslide is different, which indicates that the landslide event significantly changed the local topography and geomorphology. This study provides an insight into the spatiotemporal evolution of the landslide and has practical importance for early warning of landslides and risk mitigation.