ABSTRACT: An overview of recent large landslides in northern British Columbia, Canada.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Within the last few decades, at least twenty-four, long-runout rapid landslides, each in excess of 1 million m 3 , have occurred in northern British Columbia. Fifteen of the landslides have happened within the last 10 years alone. The landslides include low-gradient rapid flowslides in cohesive sediments, rock avalanches, and complex rock slide - flowslides and rock slide - debris flows. The flowslides have occurred in a variety of sediments, including glaciolacustrine deposits, clay-rich tills, and clay-rich colluvium. The rock failures have involved weak shales overlain by sandstone, and volcanic rocks.We are cataloguing these landslides in a compendium of natural hazards for northern British Columbia. Pre- and post-landslide aerial photographs have been obtained for fifteen of the landslides, and detailed topographic maps have been generated from these photographs. In addition we have determined soil properties, including Atterberg tests for six of the flowslides. The rock avalanches occur in three types of settings: (1) dip slopes in sedimentaryrocks in the Rocky Mountain foothills; (2) escarpments of flat-lying sedimentary rocks where spreading is happening; and (3) unstable cirque walls. Infrastructure and resources at risk from these types of large landslides include settlements, forest roads and highways, pipelines, fish habitat, forests, and farmland. One rock avalanche terminated within 2 km of the Alaska Highway, and a rock slide came within a few kilometres of a farm house. Most of these landslides have impounded streams or rivers, thus the hazard associated with upstream inundation and catastrophic dam failure must also be considered.

Bibliography of Canadian Geomorphology