LANDSLIDES IN WESTERN CANADIAN QUICK CLAYS

Quick clays and their associated landslides are well-documented in Scandinavia, eastern Canada, and Alaska, but remain relatively unstudied in western British Columbia. Nonetheless, many isostatically uplifted fjordal valleys in coastal BC host glaciomarine quick clays. They can occur up to 230 m a.s.l., depending on the local marine limit. A number of these valleys are riddled with flowslide scars - many of the landslides occuring on slopes less than 2 degrees.

In this presentation I give an overview of British Columbia's quick clays and associated landslides, and examine geometric controls on landslide size. This includes a detailed description of a recent landslide near Terrace, BC. The landslide was a composite earth flow - spread that involved 43 ha of material.

I also consider landslides and landscape evolution in two adjacent valleys with different bedrock geology. The Nass valley, in erodible bedrock went through valley incision rapidly and experienced most of its landsliding early in the Holocene. Kitsumkalum Valley's bedrock is more resistant. Its streams are still incising drift, and thus landslides are still occurring.

Finally I examine the effects of paleoclimate, historical climate, and future climate scenarios on temporal landslide distribution in BC's quick clays.