Objectives  A large-scale landslide occurred in Zhamunong Gully, Tibet on April 9, 2000. The landslide dammed the Yigong River and forming a dammed lake. With the breaching of landslide dam, the burst flood caused serious damage to the downstream area. The remote sensing image interpretation and interferometric synthetic aperture radar (InSAR) technique is used to investigate the surface changes of Yigong landslide before and after the event and the current deformations.

  Methods  Firstly, long period optical satellite images are used to interpret the evolution of Yigong landslide from 1968 to 2020. Then, the surface deformation of landslide area from 2015 to 2019 is obtained by InSAR technique.

  Results  Experimental results show that there are massive dangerous rocks at the top of the catchment area, and large amounts of debris accumulated in the middle Zhamunong Gully. Moreover, the source area of landslide was in unstable status, where partial area collapsed a few months before the landslide failure. Deformation map shows that Zhamunong Gully was in a stable state on the whole, but six deformation areas were still detected, among which the biggest one is located in the source area of Yigong landslide with great surface deformation.

  Conclusions  Topographic conditions, earthquake and weathering together led to the occurrence of Yigong landslide. The risk of deformed bodies in the source area is so high that continuous monitoring measures should be taken with concerning the impact of drastic changes in regional environment factors on landslide.