Avalanche Planning Checklists

Defensive Mountaineering

 

avalanche

Photo copyright: John Fairley Not all avalanches start on the slope you are crossing – this avalanche started high above the rocks to the top-right and crosses the ascent tracks to the Daubenhorn.

Nearly all avalanche accidents can be avoided. Slab avalanches are the most common. 90% of people involved in avalanches trigger the avalanche that got them.

Always look for safe slopes when choosing a route. Decisions must be based on facts, not opinions, not a desire for excitement, not wishful thinking.

You must judge the likely stability of the snowpack at three key phases of the tour:

Planning
Route selection on the day
Actual slope assessment

According to three key factors:

Snow + weather conditions
Terrain
People

Make risk reducing decisions based on these facts to choose the route. These are summarised in the Planning Checklists.

Planning

Avalanche avoidance begins at home. Plan the route taking into account predicted avalanche risk and unfavourable or endangered slopes. Make decisions based on the facts. Plan in checkpoints along the route. What will be the grounds for retreating or continuing? Decide alternative objectives for each checkpoint.

Route selection

Ask questions before setting out on the tour and at every checkpoint to confirm that conditions are as you expected. Make decisions and modify plans as necessary. Agree the plan, its objectives and alternatives, with everyone in the party.

Check equipment – that everyone has shovels, probes, transceivers – and check that transceivers are transmitting before setting out.

Actual Slope Assessment

Check snow, terrain and people continuously and decide accordingly. Use your own observations to judge the snow nearby. There may be more snow or wind than expected. The wind might increase and snow might be drifting. Be alert to alarm signs.

If you don’t know an answer, assume the worst case.

Snow and Weather

What is the predicted avalanche factor in the Avalanche Bulletin? Read the bulletin in its entirety. If you can not obtain a bulletin, are you competent to make your own judgment based on facts about the snowpack, its structure and its history?

  • How much snowfall? How cold was it whilst it was snowing? How long ago?
  • Orientation of unfavorable slopes (lee and cross slopes)? In the Alps, usually NW-N-E, but check.
  • Recent weather conditions? Wind, snow, sun, temperature, cloud cover?
  • Wind direction and how strong? Where are the deposition zones?
  • Unconsolidated snow cover? Weak layers in the snowpack? Slab? Orientation? Snow-profile and shovel-test the top 100cm of snowpack (choose a small unthreatened slope of similar orientation to the main slope).

Beware of strong midday sun warming slopes and cornices above, especially west-facing slopes.

Terrain

Check the steepness of the slopes that affect the tour. Which slopes these are depends on the risk factor:

  • Factor-1 (Low risk) Only the slope in the immediate vicinity of the track.
  • Factor-2 (Moderate risk) Consider slopes up to 40 metres away from the track.
  • Factor-3 (Considerable risk) The entire slope and the run-out area are threats. Avoid slopes of 30° or more. Keep well clear of the steepest regions of the entire slope. Even flat run-out slopes are endangered by slopes above them. Beware of terrain traps behind mounds or moraines where deep avalanche accumulations can occur. Even favorable aspect slopes will contain drift snow in hollows and gullies. Space out 10m apart when climbing slopes of 30° to reduce the forces on the snow pack and risk of multiple burials. Descend them at 50m spacing. Inexperienced people should only travel with much more experienced leaders. The leader’s track defines the steepest line that may be skied.
  • Factor-4 (High risk) Beware the entire slope and beware of steep slopes even some distance away. Choose slopes of 25° or less. Keep well clear of all slopes over 30° and well clear of run-out zones and terrain traps. Space out 10m apart on slopes to reduce the forces on the snow pack and risk of multiple burials. Only very experienced persons should be in the party.
  • Factor-5 (Very high risk). Stay at home.

Be alert to alarm signs that can indicate a local risk far higher than the surrounding slope.

Whilst planning your route work out the inclination of the slope from the separation of the contour lines on the map. Use 1:25000 maps whenever possible. For 20m vertical interval between contours as in Swiss maps (Landeskarte der Schweitz) this equates to:

Gradient

 Scale

1:25000

1:50000

15°

3.0mm

1.5mm

20°

2.2mm

1.1mm

30°

1.4mm

0.7mm

45°

0.8mm

0.4mm

 

Between the darker 50m contours on British Ordnance Survey maps (OS have 10m intermediate contour lines), this equates to:

Gradient

Scale

1:25000

1:50000

15°

7.50mm

3.75mm

20°

5.50mm

2.75mm

30°

3.40mm

1.75mm

45°

2.00mm

1.00mm

 

Set absolute limits: 30° in NW- N- NE facing slopes when the danger is moderate (2), 30° on all slopes when considerable (3) and 25° when the danger is high (4).

Consider scenarios: what could snow conditions be like where we plan to go? Terrain traps? What might conditions be like higher up where there has been more snow and wind?

On tour judge the gradient of the slope ahead of you.

  • Observe the climbing tracks in the snow. People tend to start doing kick-turns when slopes reach about 30°.
  • Many people are uncomfortable with skiing down a slope steeper than 30° and will do kick-turns in descent.
  • Loose snow avalanches often start spontaneously on slopes greater than 35°.
  • Use ski sticks to measure the angle of the slope:
    • Use one stick to mark the length of a stick uphill in the snow.
    • Lift the lower end and dangle the other stick from it so that it touches the snow in line with the mark.
    • If it touches the lower end of the mark, (an equilateral triangle)  the gradient is 30°.
    • For every hand-grip length that the vertical stick touches the snow below/above the end of the mark, add/subtract 3°.

Be wary of avalanche cone slopes below gulleys – avalanches fall here regularly. Be wary too of sun-soaked slopes high above you even though you are in shadow . Wet snow avalanches will start on slopes of less than 25°. They travel slowly but often considerable distances with considerable force.

Decide which slopes could be unfavorable or dangerous. Maps do not show all the bumps and hollows and there might be steeper sections. Always check the steepness of unfavorably orientated slopes.

Be wary of convex slopes, funnels, gullies and hollows and slopes near the crest of a ridge. Avalanches are more likely to be triggered where the depth of weak layers of snow is shallow (50cm or less below the surface) such as near ridge crests or at the edges of gulleys and hollows.

If you do have to cross a dangerous slope, ask first if it could be avoided. Cross one at a time with everyone observing the person at risk, and cross to a place of safety before the next person crosses. Keep 10 metres apart if you have to cross suspect slopes especially near the crest of a ridge. Use the same track. Do not bunch up with other parties or try to pass them. A group of 10 people can weigh 1 tonne. In descent stay 50m apart.

Be very wary of new snow cover bridging crevasses on glaciers. Rope up and use an avalanche probe to probe the surface ahead and around you. Do not gather together for rests and photographs in crevasse zones.

People

Always take time to reach decisions. Only decide once all information has been gathered.

  • How enthusiastic are the others? Raring to go? Excited? Resist peer pressure.
  • How far have people come? Is this their only chance this year? Resist pressure from goals and itineraries.
  • Suppress personal ambition and pride.
  • Other groups nearby? Resist implicit or explicit competition to ski virgin slopes.
  • How strong is my group? How experienced?
  • Other parties, above, below? Are they behaving responsibly?

Maintain contact with all members of the group especially in poor visibility. Do not allow the group to split nor let anyone fall behind. Ensure the the most experienced person is at the front and make sure that at least one strong person brings up the rear to look after the back markers. Maintain contact with the tail.

Avoid the situation where people that are less skilled in assessing snow stability or in selecting routes in avalanche terrain migrate to the front of the group. Those behind, even if experienced, often just follow the track, paying little attention to terrain or snowpack.

Adjust speed to suit the slowest. The group will be stronger if it stays warm by moving slower together than if it stops for long pauses to let others catch up, becoming cold and acrimonious in the process. Change the objectives if necessary. Do not race ahead, even when the hut or the summit is in sight.

Poor visibility and whiteouts make it difficult to keep the group together and select safe routes.

At pre-planned checkpoints, cross-check terrain and snowpack. Always checkpoint before entering any steep slope even if others are skiing or snowboarding there already.

Involve less experienced people in route selection and stability assessment to build the knowledge and experience of every person in the group. Ask, “Why do we think that slope is stable?”

Combine checkpoints with breaks for chocolate and hot drinks. A party that is warm and rested will perform better than one that is tired and dispirited, cold and hungry.

Do not be afraid of changing plans.

If caught

SHOUT! – TRY TO ESCAPE – GET RID OF GEAR – TRY TO STAY ON TOP –  AS AVALANCHE STOPS TRY TO POKE THROUGH TO THE SURFACE – CLEAR SPACE AROUND FACE.

Alarm Signs

Continuously observe the snowpack and weather. Any of these alarm signs should alert you to increased risk

  • The first good day after heavy snow
  • Very cold when snow was falling
  • Spindrift
  • WUMM! sound
  • Snow settling under skis
  • Snow breaking up and sliding away at turns
  • Cracks in the snow
  • Lots of new snow on trees
  • Heavy snowfall still falling
  • Poor visibility so steepness of slope can not be seen
  • Lee slope
  • Convex slope
  • Close to ridge crest
  • Fresh snow ripples, dunes and other signs of wind
  • Strong wind? Drifting? Plumes of spindrift
  • Fresh avalanches, especially slab avalanches, which slopes and orientation
  • Sudden rise in temperature.

Two or more alarm signs together mean Avalanche Risk Factor 3 (Considerable) or greater.

Absence of alarm signs does not indicate a lower avalanche factor than forecast.


This guide is provided solely as an aid to mountain safety. Actual conditions can be other than they appear. This guide does not replace an individual’s responsibility to take account of all pertinent factors and to exercise due diligence in reaching decisions. Neither the Alpine Ski Club nor its office bearers accept responsibility for decisions taken by individuals or groups as a consequence of using this guide.

The information on this page is based on much valuable work done by the avalanche research associations and institutes of several countries, publications from Alpine Clubs in Europe and North America and on the work of Martin Engler, SnowCard & Faktorencheck, published by the DAV.

Further information can be obtained by exploring the literature and the links page on this website.

Avalanche Planning Checklists