The Geomorphology of Vancouver Island is a series of nine thematic maps, one of which is a map of mass wasting potential for Vancouver Island. This report represents a description of the Mass Wasting Potential Map and the results of analyzing the regional character of landslide potential. Vancouver Island has been divided into four major zones: the Wet West Coast, Moderately Wet Central Island, Moderately Dry East Coast, and Alpine (zones I?IV, respectively). Landslide frequencies are proposed at 0.012, 0.007, and 0.004 events per square kilometre per year for zones I?III respectively, and several times higher for zone IV. Mass movements in zones I?III are generally dominated by debris slides and debris flows averaging about 11,000 m2, but ranging nearly three orders of magnitude. The Alpine Zone (Zone IV) contains substantial areas of rock fall and snow avalanches in addition to debris slides and flows. Two sub-zones related to bedrock geology were established because of associated differences in landslide behaviour: the Island Plutonic Suite appears to be more stable under natural (typically unfractured and unweathered) conditions, but is less stable under conditions that alter the rock (e.g., road building and frost shattering), and the Sicker Group is generally less stable than adjacent bedrock types. Other geological considerations were also incorporated into the map. The impact of logging and road building on landslide frequency is considered. Results indicate that logging activities increase landslide frequencies by more than 10 times, and the presence of roads increases landslide area by 22 to 43 times. These results corroborate previous studies.
Guthrie, R. H.. 2005. Geomorphology of Vancouver Island: Mass Wasting Potential. Ministry of Environment. RR 01