Water Stewardship Information Sources

Citation Guthrie, RH. 2005. Geomorphology of Vancouver Island: Mass Wasting Potential. BC Ministry of Environment, Research Report RR01.
Organization BC MoE
URL http://www.env.gov.bc.ca/wld/documents/techpub/rr01/rr01_geom_vi.html
Abstract/Description or Keywords 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.
Information Type report
Regional Watershed Vancouver Island South, Vancouver Island North
Sub-watershed if known
Aquifer #
Project status
Contact Name Richard Guthrie
Contact Email [email protected]