Last week wePowder reported 69 deaths due to avalanches in the Alps this winter. Since “prevention is better than cure”, knowledge on avalanche risk is important for those of you who are planning to go off-piste. Besides instability of the snowpack and the presence of a trigger (human or natural), specific terrain features can increase the avalanche risk. We summarized five of these important slope features, which can help you recognize avalanche-prone terrain.
- The slope angle influences the friction between the slope and the snow layer. Most avalanches occur on slopes with angles between 35-40°.
- The exposure of a slope to the wind determines whether snow will be blown away or accumulates. On wind sheltered slopes, wind slabs can be formed, thereby increasing the risk on slab avalanches.
- The terrain shape influences where snow will accumulate (e.g. gullies, terrain breaks, large open slopes) or where the snowpack will be thin (e.g. ridges, cliffs).
- The slope orientation to the sun affects how much radiation the slope receives. The snowpack is often colder and weaker on the north face. On the south face the radiation increases the risk on wet snow avalanches, especially during spring.
- The base layer underneath the snow influences the friction between the ground and the snow layer. A smooth base layer increases the avalanche risk. Melt water can accumulate on firm base layers, making these slopes more prone for a glide avalanche.