Switzerland: New maps illuminate avalanche terrain

Terrain features, such as slope angle and topography, are crucial factors in the assessment of avalanche danger. Using only a topographic map to understand the terrain is not easy, even for experts. For this reason the SLF has developed maps covering the territory of the Swiss Alps that illustrate where threats of typical skier-triggered avalanches exist.

Slab avalanches most frequently start on steep, slightly convex slopes with a gradient of 35° to 40°. The classified avalanche terrain (CAT) map indicates potential starting zones, remote triggering and runout zones. The avalanche terrain hazard (ATH) map shows the general danger posed by avalanches.

The maps depict avalanche situations in which small to large (Size 3), but not very large, avalanches are to be expected. Differences in aspect and altitude zone, as well as terrain with a gradient of more than 50°, are disregarded, as are the current weather/snowpack conditions, the extent of danger, or the avalanche problem. In this respect the maps are static and ignore the current avalanche danger. 

The new maps provide a good basis for interpreting the avalanche terrain and facilitate both tour planning and route selection. They also allow crucial spots to be recognised and assessed more easily. Availability is as follows:

• Integrated in the White Risk tour planning module TOUR (online and app) as layers, and available to users with a standard licence
• At the Maps of Switzerland website:
  • Classified avalanche terrain (CAT) map
  • Avalanche terrain hazard (ATH) map