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Avalanche avoidance

It is rarely essential to negotiate an avalanche-prone slope. It is usually possible to find another way, or retreat. 90% of avalanches involving human subjects are triggered by their victims.

If it is essential to proceed, the following should be borne in mind:

  • Solo travellers in avalanche terrain run particularly grave hazards
  • Skiers are in greater danger than walkers - the lateral cutting action of skis readily releases unstable snow. All off-piste skiers should use avalanche transceivers and have them switched on before leaving base. They should carry collapsible probes and shovels. Climbers and walkers should consider the use of these items
  • Direct descent or ascent is safer than traversing
  • Go one at a time – the others should closely observe the progress of the person on the suspect slope
  • Belay if possible, although this is rarely feasible on wide, open slopes

Avalanche checklist - Top 6 factors

  • Visible avalanche activity. If you see avalanche activity on a slope where you intend to go, then go somewhere else.
  • New snow build-up. More than two centimetres per hour may produce unstable conditions. More than 30 cm. of continuous build-up is regarded as very hazardous.
  • Slab lying on ice or nevé, with or without aggravating factors such as thaw.
  • Discontinuity between layers, usually caused by loose graupel pellets or airspace.
  • Sudden temperature rise. The nearer this brings the snow temperature to zero degrees Centigrade, the higher the hazard, even if thaw does not occur.
  • Feels unsafe. The ‘seat of the pants’ feeling of the experienced observer deserves respect.

The Chalamain Gap, deeply filled with avalanche debris

A terrain trap is a topographical feature on the mountainside. Classically it can be a depression, concavity or flattening, such as a gully, corrie basin or abrupt change of slope angle which would allow avalanche debris to accumulate rather than flow away downhill.

Examples in the Scottish mountains would be Coire na Ciste on Ben Nevis, Coire na Tulaich on Buachaille Etive Mor, the Chalamain Gap and the moraines in Coire an't Sneachda in the Cairngorms and G&T Gully on Aonach Mor. Four of these locations have been the sites of multiple avalanche burial fatalities as a direct result of their being terrain traps.

Since shovelling takes such a long time, deep burials have a very low chance of survival. Even a small avalanche off the side of a small gully can have significant consequences if the debris has nowhere to run to. Avalanche danger will rise and fall throughout the season as the snow pack and weather conditions varies, but the topographical structure of the mountainous terrain that you choose to travel through remains constant.

The key to avoiding terrain traps is to make good route choices:

  • Plan ahead before you leave the comfort of your living room and study the terrain for your intended route on the map.
  • Always be flexible and have alternative plans.
  • Stay high: choose ridge lines and broad shoulders.
  • Avoid gullies, abrupt slope transitions and corrie basins in times of high avalanche risk.
  • Remember: it might not be you that triggers the avalanche. You could just be in the firing line.