A large rockslide–debris avalanche in cohesive soil at Pink Mountain, northeastern British Columbia, Canada

Abstract

In early July 2002, a large rockslide–debris avalanche occurred on the west slope of the Pink Mountain anticline in northeastern British Columbia (57°04′N; 122°52′W). The slopes have been subjected to previous deformation and landsliding. Pre- and post-slide digital elevation models (DEMs) were created from aerial photography. Approximately 1.04 M m 3 of sandstone and shale travelled nearly 2 km from an elevation of 1460 m to 1010 m. The landslide has a fahrböschung of 11.6° and covered 43 ha. The rock debris entrained a certain amount of fine-textured till and colluvium increasing its volume by 15%. This entrainment caused partial liquefaction of the underlying soil thereby enhancing the mobility of the landslide. We used a Bingham rheological model to dynamically model the landslide with excellent correspondence between the analysis of the actual observed behaviour of the landslide.