Avalanche glossary
Decision-making strategies
Act clever for your own safety
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Decision-making can be defined as examining, choosing, and carrying out options.
When assessing avalanche risk, the so-called '3 × 3 Filter’ (und Reduktionsmethode) by Werner Munter is a probabilistic strategy of decision-making for the assessment of avalanche risk. Here, the three avalanche factors are looked at through three regional filters.
The aim of the 3x3 filter method is to minimize the risk of triggering an avalanche as much as possible. In practice, this means to work out whether a certain slope is safe to travel on.
The three avalanche causing factors:
1. Conditions (snow and weather)
2. Avalanche terrain
3. People (person moving in the terrain)
can be viewed from three different perspectives:
1. Regional
2. Local
3. Zonal (individual slope)
1. Always start with a regional assessment of avalanche
risk. Thanks to avalanche bulletin reports and weather forecasts we are aware of the general danger levels in the region.
2. For the assessment of a local area, constant observation of our surroundings can help us to identify possible danger zones.
3. When evaluating individual slopes for a descent, look at the terrain for clues of potential avalanche danger.
When looking at the three avalanche-causing factors for each of the three respective perspectives and 9 times come to the conclusion that conditions are safe, a slope is safe to descent. If, on the other hand, one or more times we come to the conclusion that conditions are unfavourable then we do not descend, otherwise we put our lives at risk.
The 3x3 filter method resembles a system made up of three stacked safety nets. The smaller the area that needs to be evaluated, or the less the distance, the finer the meshing of the safety net and the smaller the risks involved.
The sequence of assessment is important. Always start with a regional assessment (preparation), followed by the local evaluation (area assessment) and finally look at the individual slope.
The 3x3 Filter method is only one of several methods than can be used to assess avalanche risk. The most important are:
When assessing avalanche risk, the so-called '3 × 3 Filter’ (und Reduktionsmethode) by Werner Munter is a probabilistic strategy of decision-making for the assessment of avalanche risk. Here, the three avalanche factors are looked at through three regional filters.
The aim of the 3x3 filter method is to minimize the risk of triggering an avalanche as much as possible. In practice, this means to work out whether a certain slope is safe to travel on.
The three avalanche causing factors:
1. Conditions (snow and weather)
2. Avalanche terrain
3. People (person moving in the terrain)
can be viewed from three different perspectives:
1. Regional
2. Local
3. Zonal (individual slope)
1. Always start with a regional assessment of avalanche
risk. Thanks to avalanche bulletin reports and weather forecasts we are aware of the general danger levels in the region.
2. For the assessment of a local area, constant observation of our surroundings can help us to identify possible danger zones.
3. When evaluating individual slopes for a descent, look at the terrain for clues of potential avalanche danger.
When looking at the three avalanche-causing factors for each of the three respective perspectives and 9 times come to the conclusion that conditions are safe, a slope is safe to descent. If, on the other hand, one or more times we come to the conclusion that conditions are unfavourable then we do not descend, otherwise we put our lives at risk.
The 3x3 filter method resembles a system made up of three stacked safety nets. The smaller the area that needs to be evaluated, or the less the distance, the finer the meshing of the safety net and the smaller the risks involved.
The sequence of assessment is important. Always start with a regional assessment (preparation), followed by the local evaluation (area assessment) and finally look at the individual slope.
The 3x3 Filter method is only one of several methods than can be used to assess avalanche risk. The most important are:
- Snowcard by the DAV (Deutscher Alpen Verein). A visual illustration of risks involved, taking into account steepness, aspect and danger level, and with recommendations on how to behave accordingly (www.av-snowcard.de)
- Stop or Go by the OeAV (Oesterreichischer Alpenverein). Gives advise on whether to “stop or go” resulting from checks based on the avalanche bulletin report combined with avalanche factors, with recommended standard measures (www.alpenverein.at). It is better to master one method well, than to just know many.]
- The Reduction method by Werner Munter: Calculation of risk using the factors steepness, aspect, danger level and behaviour (info at: Munter, W. (2003) 3x3 Lawinen. Risikomanagment im Wintersport, Garmisch-Partenkirchen)
