LANDSLIDE SUSCEPTIBILITY MAP OF CANADA

Within Natural Resources Canada (Geological Survey of Canada), one objective of the Public Safety Geoscience Program is the provision of broad, high level information that summarizes the likelihood of threat from a variety of natural hazards to Canada’s citizens and infrastructure. Landslides are especially important. In Canada, during the past 150 years, more individuals have died from landslides than all other natural hazards combined. Moreover, landslides are estimated to cost (direct and indirect) the country over $200 million (CDN) annually. Unfortunately, no publically available, pan-Canadian expression of the potential threat from landslides currently exists. In response to these facts and issues, the Geological Survey of Canada has now developed a national scale (1:5 million) landslide susceptibility map to illustrate the significant variability that exists across the country with respect to the likelihood of slope instability.

In the absence of a national inventory of landslides, information used in the derivation of this map (GIS based) consisted of national scale data for the following parameters: vegetation, precipitation, permafrost, aspect, slope angle, distance to rivers, distance to coast (lakes and oceans), bedrock geology and surficial geology. Attributes within each parameter were assessed and classified (semi-quantitatively) according to several categories of significance (1-low to 6-high). For the classification, expert opinion was obtained during a workshop at which GSC landslide experts relied on their personal experience and professional knowledge as input to the attribute and parameter relevance regarding landslide hazards.

The final map, to be released as a GSC Open File map, provides an excellent “first approximation” characterization of landslide susceptibility for the diverse terrain scattered across Canada using a hot to cold (red to green) legend to illustrate the threat. At this scale, the classification is most useful in demonstrating regional trends. Local and site specific assessments cannot be reliably extracted from such a national scale map and require more diligent study and interpretation on a case by case basis.