Decision strategy (avalanche)

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Ski tour in unsecured, alpine terrain

Decision-making strategies serve to assess the avalanche risk and are vital for many winter sports enthusiasts . They facilitate and simplify the handling of the complex and potential danger of avalanches in the winter, alpine mountains. However, even with these methods, the risk of an avalanche cannot be completely ruled out.

In the meantime, these methods have become generally established in alpine winter sports. They are available in almost all ski areas, summarized in leaflets, at the lift stations. Many alpine clubs and mountain schools teach using these methods.

Theoretical foundations

In the past, assessing the avalanche danger was the task of experts who assessed the snow cover on the slopes based on various factors.

This classic analysis was flawed for several reasons. Very complex processes take place in the snowpack that hardly allow a reliable forecast of the avalanche danger. In addition, the lack of in-depth knowledge and the subjective perception of the factors by humans prevented a reliable prediction of the actual avalanche danger.

Werner Munter recognized this and developed a holistic risk management system based on statistics and empirical values; the formula 3 × 3 and the elementary reduction method. This created the first strategic method for assessing the avalanche risk.

The risk can never be eliminated, even with scientific methods. There is always a residual risk. People have to learn to make a “yes / no” decision on this basis of uncertain knowledge.

In summary, this means that the relationships between avalanche formation are very complex and cannot be recorded individually with the necessary accuracy. Probabilistic methods do not go into detailed questions, but use the experience expressed in probabilities. It turns out that in practical application, the assessment of a few risk factors is sufficient. In contrast, the assessment of an isolated individual factor is not expedient.

Formula 3 × 3

The formula 3 × 3 results from the assessment on three different levels (regional, local, zonal) based on three main factors (conditions, terrain, people) . The levels act like a kind of filter, with the subdivision into coarse, medium and then fine . You proceed step by step, the order must not be changed. According to Munter, the regional filter filters out approx. 40% of all possibilities, the local filter another approx. 25% and the last zonal filter approx. 10%. This results in the following formula:

Example:

or

The three-stage criteria and filters are shown in a 3 × 3 matrix. Weighted with the probabilities found, this results in the formula 3 × 3:

level Conditions terrain human
Regional (tour planning) Avalanche report (LLB), weather forecast, expert information Map, guide books, photos, own terrain knowledge Participants, equipment, skills and experience, leadership
Local (on site) Snow conditions, review of the LLB, weather (visibility, wind, precipitation, temperature) Assessment and verification with my previous presentation Participants, other groups, equipment control, check schedule
Zonal (on the way / individual slope assessment ) Fresh snow, drifting snow, visibility, irradiation, catchment area of ​​snow slabs Orientation: Who or what is above / below me? Steepness, exposure, proximity to the ridge, altitude, slope shape Leadership tactics / precautionary measures, stamina, technique

Lively comes to the conclusion that “the avalanche danger must never be assessed on the basis of just one main factor (criterion), but all three main factors must be included in the holistic risk analysis”.

In the application, the respective criteria are enlarged like a zoom from level to level; hence the name zoom system. The formula 3 × 3 is first of all an actual value analysis of the residual risk. The weighting of the individual factors immediately shows the user where the greatest potential for improvement lies and puts special measures into perspective accordingly. Nevertheless, through further decision-making strategies, the risk potential given by the formula 3 × 3 can be further reduced by specifically reacting to the risks previously identified in the analysis. Decision-making strategies are an integral part of the planning and implementation of alpine winter sports activities.

All other published decision strategies are based on or similar to the risk management system of the formula 3 × 3 . Essential factors in the strategic decision-making process are the danger level of the avalanche report (LLB) and the slope of the slope as well as the slope exposure (e.g. a north-east slope). The avalanche risk is evaluated using scales, graphics or simple calculations. This can be done in the route planning as well as in the individual slope assessment. The embedding of this risk analysis as it is e.g. B. offers the formula 3 × 3 in a risk management system. Because the question is ultimately how to deal with the residual risk.

The individual methods are shown in the following. It is not a guide to their use, dealing with the respective decision-making strategy must be learned in practice.

Reduction method

The reduction method is a "planning and control instrument " which essentially complements the 3 × 3 formula . It was also developed by Munter with the aim of further reducing the residual risk of 1%, which remains when using the 3 × 3 formula .

Munter differentiates between the elementary reduction method and the professional reduction method . The elementary reduction method is offered in a modified form as a graphic reduction method (GRM) by the WSL Institute for Snow and Avalanche Research SLF .

Elementary reduction method

The elementary reduction method defines a slope limit value for each danger level of the avalanche bulletin , which must not be exceeded. Depending on the danger level, the maximum incline in the immediate vicinity of the planned route or the entire slope is decisive. For slopes outside the critical area of ​​the management report, a lower danger level and thus a higher slope limit value may be assumed.

Professional reduction method

The professional reduction method is more flexible, but its correct application is also much more demanding. In the professional reduction method, the risk is assessed using a calculation. First, an assessment of the potential risk is made. This is done through the avalanche report and / or through your own assessment on site. An attempt is made to minimize the residual risk equal to or below 1 using reduction factors. The formula is as follows:

The hazard potential is the sum of the hazards in the respective area. The growth of the danger occurs exponentially. It is possible to make intermediate gradations such as hazard potential 3 between low and moderate. The subdivision is as follows:

  • Low = potential 2
  • Moderate = potential 4
  • Considerable = potential 8

Reduction factors are divided into first, second and third class. First-class reduction factors concern the slope. The lower the slope, the higher the reduction factor and vice versa. Second-class reduction factors relate to slope exposure (slope alignment) and are based on statistical principles. A higher or lower reduction factor is chosen depending on the exposure. Third-class reduction factors are further means, such as B. small groups, walking at intervals, etc.

SnowCard

Front SnowCard
SnowCard back

The SnowCard was developed by Martin Engler and Jan Mersch . Both are mountain and ski guides and trainers in the federal teaching team of the German Alpine Club (DAV) . This decision-making strategy has its origin in the factor check and uses the so-called avalanche risk check as a strategy. In the meantime, the DAV has acquired the rights to the SnowCard. It now bears the name DAV-SnowCard .

The SnowCard has a wobbly image on one side which, when tilted, shows two different graphics that divide the average avalanche risk into favorable and unfavorable slope exposure (slope orientation). Furthermore, the risk is displayed on the basis of flowing color transitions from green to yellow to red. Green stands for a low risk and red for a high risk. The map has a Cartesian coordinate system for this purpose . The slope steepness is shown on the axis (longitudinal axis) and the current degree of danger of the avalanche report on the axis (transverse axis). Based on the assessment of the steepness of the slope, the slope exposure and the degree of danger, the risk can now be read within the graphic.

Step-by-step instructions for using the SnowCard are shown on the back. It also has a slope inclinometer for topographic maps and a pendulum for measuring slope inclination in the field.

Factor check

The factor check developed by Engler is practical risk management for advanced users and professionals. It starts in the area of ​​snow and weather factors that cause avalanches and was used even before the 3 × 3 formula and the elementary reduction method were published. According to a defined process, these factors are checked individually and evaluated according to a traffic light-like color system. Similar to the Snowcard, the factor is assessed as negative or positive from green to yellow to red. Then the factors are assessed in an overall overview and a conclusion is drawn about the avalanche risk. Special alarm combinations of factors lead to a far more dangerous assessment of the avalanche situation.

factor Individual evaluation
Last snowfall period: depth of new snow, consolidation / settlement, load-bearing layers
         
Wind: wind strength, transport in combination with fresh snow, time factor, leeward or windward
         
Temperature: Current temperature / radiation, change, tendency over the last few days
         
Old snow surface : Type of conversion / degree of the old surface, layer connection in combination with temperature and time
         
Old snow depth: old, unstable intermediate layers, floating snow on the ground, degree of moisture in the snow cover
         

The factor check essentially complements the other, "simpler" decision strategies. It makes it possible to check the avalanche situation report in detail and to carry out a profound, personal assessment of the local avalanche danger. No factors should be forgotten or overlooked by the given flow chart. However, the factor check is reserved for ambitious winter mountaineers and professionals who can actually evaluate the individual factors through knowledge , experience and competence. The factor check is not suitable for laypeople.

Stop or Go Card

The Stop or Go Card from Michael Larcher and the mountain guide Robert Purtscheller is a help that is preferred by the Austrian Alpine Association (ÖAV) . The first check (one side of the map) is based on the slope limits of Munter and, depending on the danger level, subdivides the passable slopes according to their steepness. In the second check, factors causing avalanches are checked for their danger. Then the decision is made to go or not to go ( stop or go ).

On the second page of the map, standard measures for route planning and en route are offered. The subdivision is made according to the time sequence into planning, ascent, and descent and takes into account the essential factors of the 3 × 3 formula . The map also has a slope inclinometer for maps.

literature

See also

Web links

Individual evidence

  1. ^ Avalanche knowledge for skiers and mountaineers / Werner Munter . - 2nd, verb. and exp. Edition. - Bern: Hallwag, 1984. - ISBN 3-444-50158-7
  2. ^ New avalanche science: a guide for practice, Werner Munter , ed. from the Swiss Alpine Club. - 2nd, revised. and exp. Edition - Bern: SAC, 1992. - ISBN 3859021168
  3. ↑ 3 × 3 avalanches: Deciding in critical situations / Werner Munter . - Garmisch-Partenkirchen  : Pohl and Schellhammer, 1997. - ISBN 3-00-002060-8 , p. 117.
  4. ↑ 3 × 3 avalanches: Risk management in winter sports / Werner Munter . - 3rd edition. - Garmisch-Partenkirchen  : Verlag Pohl and Schellhammer, 2003. - ISBN 3-00-010520-4
  5. ↑ 3 × 3 avalanches: Risk management in winter sports / Werner Munter . - 3rd edition. - Garmisch-Partenkirchen  : Verlag Pohl and Schellhammer, 2003. - ISBN 3-00-010520-4 , p. 122
  6. ↑ SLF leaflet "Warning Avalanches!" ( Memento of the original from March 6, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.slf.ch
  7. ↑ 3 × 3 avalanches: Risk management in winter sports / Werner Munter . - 3rd edition. - Garmisch-Partenkirchen  : Verlag Pohl and Schellhammer, 2003. - ISBN 3-00-010520-4 , p. 113
  8. ^ The white danger: snow and avalanches: experiences - mechanisms - risk management / Martin Engler. - Sulzberg: Martin Engler, 2001. - ISBN 3-9807591-1-3
  9. ↑ (see ENGLER / MERSCH 2001, pp. 246–251)
  10. ↑ Michael Larcher - stop or go (2012) . Site of Berg und Steigen. Retrieved on August 28, 2015 (PDF; 2.47 MB).