Examining climate controls on recent landslides in northern British Columbia, Canada

In northern British Columbia, Canada, temperature and precipitation has been increasing since the beginning of the instrumental record in the late 1800's. These trends may be responsible for the apparent increase in the frequency of landslides in the area. We examined recent landslides in northern British Columbia for both climate causes and weather triggers. To examine for causes of slope failure, we calculated trends in total precipitation, mean temperature, and extreme maximum and minimum temperature from Meteorological Survey of Canada weather stations. To examine for slope failure triggers, we analyzed weather station data for significant temperature or precipitation amounts as well as digital weather imagery from satellites and radar where available. We found a close relation exists between climate causes and landslide type. Large landslides in bedrock occurred during years or long periods of above-average temperature. Landslides in unconsolidated sediments occurred during years or long periods of above-average precipitation. Many of the analyzed failures occurred after warm or variable winters. Where satellite imagery was available, we found convective thunderstorms or large cyclonic storms were common during the time of failure of many landslides. Long-term increases in temperature and precipitation may be preconditioning marginally safe slopes for failure and intense or large- scale storms may be the triggers of such failures.