A landslide velocity database for the Site C Reservoir in Northeastern British Columbia

ABSTRACT: The modern Peace River Valley in British Columbia contains an abundance of landslides with volumes ranging from tens of cubic metres to more than 10 million cubic metres. Landslide types in this region range from shallow slides in overburden to deep seated slides in clay shale bedrock, and often involve multi-level, complex landslide mechanisms. A landslide inventory for this region was updated by BGC in 2021 and 2022 to assign qualitative landslide behaviour types to each landslide, which reflect the dominant mode of landslide movement, long-term mean annual displacement rates, and the estimated relative frequency of faster movements. Airborne lidar change detection between 2006, 2015, 2019, and 2021 and satellite InSAR data from 2020 and 2021, coupled with select field observations, were used to estimate the velocity of landslides over each incremental date range. The velocity distributions were compared to the long-term average probability distributions (limiting state vectors) proposed for each behaviour type, which have been used to define transition matrices for Markov chain modelling of landslide velocities.