How differences between snow avalanches and other slope hazards affect mapping and mitigation

ABSTRACT: Snow avalanches differ from other slope hazards such as debris flows and landslides in ways that affect mapping and mitigation. Snow avalanches start as a result of failure in a bonded granular material in which the bonds are close to the melting point. Periods of instability are often limited to hours or days. In contrast to other slope hazards, explosives are effective triggers of unstable snow, thereby shortening periods of instability and allowing parts of ski areas or transportation corridors to be quickly re-opened. Where snow avalanche occurrences observations are available for a decade or more, this often results in better occurrence and runout records than for other slope hazards. For snow avalanches, hazard mapping thresholds based on a low annual probability (e.g. Pa ≤ 10-3) are especially uncertain and problematic for hazard mapping.