Landslide Susceptibility Mapping for Large Landslides in Sensitive Clay

Following the retreat of the continental ice sheet about 10,000 years ago, the Saint Lawrence Lowlands of eastern Canada were submerged by an abandoned arm of the Atlantic Ocean known as the Champlain Sea. The sediments deposited in this marine environment have a peculiar mechanical behaviour whereby they lose all strength upon rapid loading, resulting in sensitive fine-grained deposits that are involved in widespread incidences of large rapid landslides. Large landslides in sensitive clay in eastern Canada pose a hazard to several networks of linear infrastructure, including roads, railways, pipelines and power transmission lines. BGC was engaged by Transport Canada and the Class 1 railways, CN and CPR, to develop landslide susceptibility maps for the area.

BGC’s landslide susceptibility map was developed using GIS-based geostatistical methods. A bivariate method known as the “weights of evidence” method was applied with a wide range of geo-spatial thematic data, including surficial geology, ground elevation, slope angle, stream flow, stream gradient, depth to bedrock and local relief. The model was validated using air photo analysis for selected random location, and high susceptibility areas near railway infrastructure were checked in greater detail to rank the hazards for further study.