Defensive Mountaineering Avalanche Risk Factor

Planning Checklists

 
Ask these questions during tour planning, at the time of actual route selection on the day of the tour, and when traversing individual slopes during a tour.

Check the three key factors that affect avalanche risk, snow+weather, terrain, people, at every step asking at least the questions in the table below. The answers to these questions and your own competence and knowledge determines your decisions.

There is no absolute standard. What might be safe for a highly skilled group that takes every precaution and modifies its behaviour and route according to the risks would be absolute folly for an inexperienced group quite unable to do this.

If in doubt, assume the worst case.

There is no such thing as zero risk. Hoar frost and graupel layers can persist in the snowpack all winter long with a correspondingly high slab avalanche risk throughout the winter even though all other factors might suggest otherwise. Check.

Route Selection Checklist

Snowpack/Weather Terrain People
Tour planningPlan in checkpoints and alternatives. Avalanche Bulletin.
Weather forecast.
Information from locals.
1:25,000 Map.
Gradients from map
Guide books.
Photos.
Own knowledge.
Size of group ?
Motivations?
Expectations?
Skill level?
Equipment.
Who responsible?
Route selectionUse checkpoints and alternatives. Avalanche Bulletin Risk Factor and type of risk.
First day after new snow? Fresh snow still on the trees?
Temperature?
Actual snow conditions. WUMM sounds?
Wind direction?
Drifting?
Avalanches?
Oddities.
Visibility.
Check terrain on sight.
Gradient.
Terrain traps.
Existing ski tracks
-how many? How old?
Orientation, steepness of risk slopes.
Reports from others.
Who’s in my group?
Competitive atmosphere?
Time plan for tour?
Itinerary left with someone?
Backmarker.
Appoint possible search leaders and stress need for discipline.
Check all transceivers transmitting before leaving the hut/car.
Individual slopes during the tourGo / No Go How much new snow?
Signs of wind?
Lee or windward?
Visibility?
Solar radiation?
Temperature?
Snowpack stability?
Possible slab risk?
Alarm signs?
Actual gradient?
Steepest part of slope?

Risk Factor What slope is important?
1 on slope nearby
2 slope up to 40m away
3 over whole slope
4 whole slope and runout areas

At factor 3 limit route to 30° slopes maximum.
At factor 4 limit route to 25° slopes maximum.
What’s above me?
What’s below me?,
Convex slope?
Near the ridge?
Any wind pockets?

How many people on the slope?
Do not be pressured by presence of other groups.
Group discipline?
Tiredness?
Technique?
Spacing?
Think!

 

Risk Assessment Checklist

Low risk Some risk Moderate risk Considerable risk Very high risk Very high risk
Snowfall
Depth of new snow 0cm 10cm 20cm 40cm 80cm 160cm+
Time since last snow 4 weeks 2 weeks 1 week 4 days 2 days 1 day
Wind
Strength No wind Light wind Strong wind, Heavy drifting Storm
Lee or windward? Windward slope Wind dunes, Wind ripples Lee slope
Time since last wind 4 weeks 2 weeks 1 week 4 days 2 days < 1 day
Temperature
during snowfall 0° C -2° C -4° C -8° C -15° C -25° C
Temperature change Increased to 0° C for >2days Midday, Full sun Increased to 0°C in last hours.
Föhn
Snowpack
What surface below new snow Old consolidated snow Fine powder Powder Crust Firm Ice Loose snow, Hoar frost
Old snow structure Stable fine crystal layers Frozen snowpack (becomes wet and dangerous
in sun)
Wet ground (grass), Warm, wet snowpack Graupel or Hoar frost between layers.
Terrain
Gradient of slope <20° <30° >30° > 40°
Form of slope Flat, No bumps or gulleys Concave, Many old ski tracks Convex Near crest of ridge, Gulley, Funnel
Group
Fully trained, Analytical, Disciplined Other groups skiing powder nearby Excitable, Excited, Competitive, Targets

Defensive Mountaineering Avalanche Risk Factor