Assessing landslide occurrence with snow data and other site information

In early April, 1985, large landslides occurred at several low elevation forested locations iN south central B.C. causing damage to railroad and fish habitats with economic and legal implications. The causes of these landslides were assessed using snow and temperature data as well as other site information. Field inspections revealed that several features combined to make these locations very susceptible to mass wasting. These features include steep and convergent slope, shallow soil with high density subsoil, and the evidence of scars from uprooted trees by previous windthrow. However, these landslides were considered to have been mainly triggered by an extraordinary climatic event that provided an extremely large amount of water to the soil. Analyses of snow course, snow pillow and temperature data indicate that this climatic event in fact produced record-breaking snowmelt water (380 mm) at these low elevation locations.