Mapping a northwestern regional hub to determine risk tolerance for flowslides and other types of landslides

Terrace Landslide Hazard and Risk Mapping

Terrace is a northern British Columbia community nestled among beautiful rivers and high mountains. Terrace’s landscape includes the presence of sensitive marine clays, and consequently, a pending threat of flowslides (a special type of low angle, sometimes less than three degrees, landslide associated with the disturbance of marine clays). Our client approached us to determine the likelihood of flowslides within the footprint of a proposed development.

To satisfy development approvals, we faced stringent criteria where developable land was limited to areas with potential hazards of less than one in 10,000 per year. Using up-to-date LiDAR (light detection and ranging) to conduct a survey, our team of geohazard specialists created a detailed geomorphic map covering 65 square kilometres of terrain to differentiate areas that have been largely stable or unstable since the last glaciation (approximately 13,000 years ago). Using this detailed map, they determined the probability of landslide occurrence by adapting our published methods and research from Alberta, Quebec, and Norway, to determine limits of hazard for landslides in sensitive clays.

Our team provided a clear and concise report, supported by published research and geomorphological maps, to help our client understand a complex problem. The result? By identifying potential hazards in the proposed development area, we helped the community know where they could safely build.