R. Lienerth, R. Bednarik, The. Nádvorník, On the. Kořízek (2004), www.lezec.cz
Photo: Stock R. Lienertha, R. Bednarik and materials in. Kořízka

Decision-making strategies and methods for assessing the avalanche danger

International scale avalanches
It has five degrees. It is now a standard used throughout the world. It provides an approximate picture of the avalanche situation in the region.

1. Low risk – 1/3 winter, minimize risk, well-hardened snow. Landslides avalanches increased risk only when additional loads on very exposed slopes. Spontaneous movements of snow exceeding category splazů.
2. moderate hazard – 1/3 winter, usual situation, quite well hardened snow. Landslides at increased risk of avalanches additional load on the exposed slopes. Potentially low risk of spontaneous avalanches.
3. significant risk – 1/4 winter, Many slopes show moderate to low stability, landslide and avalanches can initiate low additional load. Occasionally spontaneous avalanches are possible medium-sized, that can intervene and frequently visited areas, as access roads, or slopes. Options hikes very limited and only with considerable experience.
4. critical situation - Only a few days during the winter, generally very weakly reinforced snow. Avalanche probability is very high even at a slight additional load. Options hikes quite limited, situation requires expert evaluation. Potentially high risk of spontaneous avalanches intervening valley areas in the medium to large scale.
5. catastrophic situation - Completely unstable snow cover on an unprecedented scale, spontaneous avalanche of epic proportions affect inhabited the valley from the relatively gentle slopes. Tours impossible, obydlí zajištěná doporučuje is neopouštět.

The term refers to any additional loads other loads slope outside layer of snow lying on it. So skialpinist climber or are already overloading. In the case of, that you go up the slope on skis, and you fall down, strain on the slope of approximately five times, how would you have demands on the space.

Generally considered the most dangerous 2. and 3. degree of avalanche danger, where they become 2/3 avalanche accident.

Decision-making strategies to start hikes and changes in its course

Stop or GO
The method developed by a team of M. Larchera. It belongs to the most basic decision-making strategies designed primarily for beginning climbers and skialpinist.
It is based on two risk assessment. Regional - the degree of avalanche danger in the area and then the zonal - watch selected phenomena in our surroundings, based on the occurrence of these phenomena, then decide, whether to go, or change the destination, or terminate a hike.
The occurrence of the phenomenon does not command a hike ukočit, But always call for a thorough evaluation of its occurrence. Of course, otherwise we will evaluate 10 cm of fresh snow with no wind and quite otherwise we will evaluate the occurrence of popping sounds and a slope, after which we. See. basic errors about avalanches, Montana 2002!!!!

Czech version of the card issued to Stop or Go Public and ČAHV

Stop or Go strana 1


Stop or Go strana 2

The main disadvantage of this decision-making strategy is reliance on the degree of avalanche danger stranger is usually designed for the whole area. Each level is assigned a value of slope steepness, but we are at stage 4 avalanche danger for the slope to the slope 30 degrees?
The second part is then necessary to realize, that the answer to the question lies in the triangle "Knowledge - Experience - Responsibility". This means, that the final decision, whether to go, or stand, is only for you.

Nivo test
This is a decision strategy presented in the life of France Robert Bolognese.
Stejně jako Stop or Go, This card is intended primarily for the general, So not quite an expert group of users, who have a basic awareness of avalanches, but did not deal with the issue in detail.
Nivo test je zodpovězení založen that was 26 precisely targeted questions, which disregarded danger of avalanches or other information provided by a foreign person. But this is offset by the necessity of your increased ability to observe and evaluate the situation in your area. Again, we face a problem of "Knowledge - Experience - Responsibility".
On each of the issues truthfully answer either YES, or NO. Every answer is YES, then adding the appropriate number of penalty points on your credit. Final credit will then assign a value, which clearly indicates, jak to your pokračováním Vasi's túry. The disadvantage is, conclusions card provides up to us during the tours, so we can become, we will not be able to alternate targets, while in the valley next to (less steep, less threatened), However, where that day can not make it longer to get, could also work under the same conditions.

The level of the test side 1

The level of the test side 2

Jak karta STOP or GO, and NIVOtest have multiple versions of design appearance. The difference is mainly in food of both cards as ratio scale tendencies to read contour lines on maps,SOS phones in Europe, or in the country, where the card was issued, basic information on the types of snow, or link to websites with mountain news.
More important than the result, that you both NIVOtest, tak i STOP or GO poskytne, the fact, that you learn on the tour watch variable factors in their environment, and these automatically internally evaluate. This has its importance, particularly at decision-making strategies for advanced 3×3 and reduction methods. Or strategy Stephan Harvey - Avalanche risk (http://www.slf.ch/info/LawRisikoBulletin.pdf), that in our country especially among a broader range is not known.

3×3
The method developed by Werner Munter group in Switzerland. Partly, this method coincides with the method Stop or GO. It is based on an evaluation of factors influencing the formation of avalanches in three dimensions and in terms of the tours at three levels.
In terms of assessment and planes always evaluate three criteria:
- conditions
- in
- one.
In terms of levels of the tours will evaluate these criteria in three phases:
- stage of preparation and planning - regional filter
- start-up phase Tours - local filter
- stage during the tour - zonal filter.

3×3 is a safety net woven of many interrelated factors involved three main criteria for the emergence of avalanches, their evaluation, still further update.
· Regional Filter - preparation at home, evaluation of available weather forecasts, state conditions, group size and prowess of its members, determine potential routes and consideration of the risk, any correction path by detecting data
· Local filter - made after arrival in, confirmation of the intended route, or, conversely, the change based on re-inspection equipment, current condition of the group members, weather and conditions. Is anyone else in the same area, outside my group?
· Zonal filter - continuous evaluation of terrain, determine slope stability, what is happening around me. Still monitor the situation around and not rely blindly on the data collected eg. at the start of tour.

3×3 tells us, whether to go on tour or not, but it will help focus our attention on the essential factors, which may potentially threaten our security.

Reduction Method
Again, the method developed by W. Munterem. It is invaluable especially in regional decision-making phase of the filter. As one of the methods can be concrete results, recommend a hike, or not, no longer just a regional phase filter, So based on the information, available to us during the preparation. In combination with the method 3×3 is almost unmatched combination. As with Stop or Go is not a factor to be considered as an element of avalanche danger inserted by someone other!
Again we evaluate several criteria - reduction factors in relation to the degree of avalanche danger. Each factor of each criterion and the degree of avalanche danger in the decision process is assigned a value. After substituting values ​​into the formula then the result will recommend a hike, or not.

Avalanche danger
degree 1 – 2
degree 2 – 4
degree 3 – 8
degree 4 – 16
degree 5 – 32

Reduction Factor of First Instance - the steepest slope site
30 degrees – 34 st – 4
35 st – 3
36 st – 39 st – 2
over 40 st – 1

In the case of the necessity of climbing switchbacks for output without wasting stick reaches the slope angle 28 – 30 st . Slopes, where there are Seypa, beyond the generally tend 39 st. To destrmine the slope can also use the so-called. Pendl trick with chopsticks (see Fig. above, page 2 BLUE CHEESE Czech version of the test). Fully optimal and most accurate is the use of clinometer.

Put the wand on the slope to compensate for minor irregularities. The wand attach the inclinometer and subtract the corresponding value.

Reduction factor of second-degree – slope exposure(orientation to the world)
area 1 NW - NE - 1
area 2 SFE - NW and NE - SE - 2
area 3 JV - SFE - 3
move beyond the potentially lavinézní slopes – 4
often riding the slopes – 2

Exposure to the slope and the corresponding reduction factor

This reduction factor is chosen with regard to the Alpine region and follows the form of a reduction method should be applied only in the Alpine region. In the area of ​​Slovakia, flow of air masses is somewhat different, and therefore is currently considering a reduction factor of this process just for this area.

Reduction factor of the third degree - the size of the group
large group without a spacing (5 more) – 1
large group with spacing (5 more) – 2
small group without a spacing (of 5 people) – 2
small group with a spacing (of 5 people) – 3

Model No. example. 1.:

8 (avalanche danger 3. degree)
____________________________
3 (35 Wed steepest slope in place) x 3 (SW slope) x 3 (small group with a spacing)

8
____________
3 x 3 x 3
= 8/27 = 0,3
0,3 < 1 => The. K.

Model No. example. 2.:

8 (avalanche danger 3. degree)
______________________

2 (37 Wed steepest slope in place) x 1 (S svah) x 2 (large group with spacing)

8
____________
2 x 1 x 2
= 8/4 = 2
2 > 1 => K. The.

definitely not to implement hike, or change the destination

Determination of snow profile
Dig a hole to the surface snow layer, maximum-length. Individual climate phenomena appear to us in layers of snow. Draw conclusions from the determination of snow requires a relatively high profile and experience as well equipped as the magnifying glass, or scale the size of snow crystals.
Usually this test is performed extensively in combination with another, So test hardness test and a sliding block.

Determination of hardness of different layers
This test is used to determine consistency between the various layers and the differences between them. It is considered one of the tests, perhaps the most damning findings of slope stability and also the simplest. This test is done while working in avalanche-prevention as a priority in the first place. We should remember, that wall of snow, on which the test is performed, as far as possible in the shade (as in 90% associate with a sliding block, it is not always possible). Horizontal lines are then highlighted the different layers of snow profile, where we recognize the different hardness of the snow, as shown in Table. Essential for us especially the interface between layers. If you find, that between two adjacent layers of the difference is more than two degrees (viz. loss. below), means it has greatly increased the potential risk of avalanches. Again, however, play the role of other factors, we can take into account, as we will show further. The test is done that way, that we are trying to sink into the snow variety of subjects, which are characteristic of each layer hardness.

Determining the hardness of the layers of snow on the ground:

Hardness	Hardness test by pushing the subject
Very soft	Fist
Soft	The four fingers
Moderately hard	One finger
Hard	The tip sticks (pencil)
Very hard	Knife
Compact ice	Neprůrazné

Fist


The four fingers

Finger

The tip sticks (pencil)


Knife

Always try hardness in the glove. The subject should go to push the snow layer freely, Not brute force!!!

For clarity and easier understanding we present two examples. Model of the. Kořízka and a particular.

Model storage layer hardness and Marking of potential risk

Specific deposit layers of 29. 2. 2004 Zlomiska, High Tatras. Gradually fell further 20 until 30 cm of fresh snow without warming, in combination with the wind then was the difference between the three layers – fist - tip sticks – avalanche situation, that about four days later claimed the life of a side valley Mengusovská.

29.2. 2004 Zlomiska, High Tatras

Test a sliding block

1) find a place, the most appropriate slope, exposure and if possible altitude slope ,as the route of our hike. Instead we choose to, we are not any threat of potentially dangerous avalanche slopes near, or for us was no longer dangerous rise, where we stand.
2) vyhloubíme pit width 1,5 – 2 m, best on ground, or max. -length, so that by closing above the snow profile was oriented vertically.

In place of the upper vertical wall let the digging probe, We can determine the height of the overall snow layer to the substrate and thickness of each layer

3) At this stage usually will put layers of hardness test
4) sides, at a distance corresponding to the length of our skis ( ca 1,5 – 1,8 m) from each side dig trenches up to the substrate 1,5 m up the slope toward the slope.
5) at the end of ditches, perpendicular to the slope of snow cut off saw, Knotted loop with or (5 m prusik) own block

Knotted loop is more difficult pruned any harder vrsvy, advantage over the pile, however, weight

6) block is ready to test

Plus or minus a few centimeters, we have always come to this form –

Evaluation test
1) block slides during digging the pit face
2) block slides during digging of side ditches
3) block pushes the cut
If a case 1 – 3 do not enter the slope and changing hike!!!
4) block pushes the start-up skiers
5) block pushes the swing in the skiers knees (slight hop)
If a case 4 – 5 is considering the continuation of tracks while maintaining the maximum vigilance, in the case of larger groups always prefer to choose a less ambitious goal, and I avoid the slopes with a gradient across 30 degrees.

The block slid on his knees in the swing, in this case, the tour continued to consider, while maintaining the maximum vigilance

6) Block the slides with a significant hop-country skiing
7) block pushes the swing in Boots
block slides down while jumping in boots

If you block this tack, gives rise to be considered quite stable

In the case of 6 – 8 slope can be considered safe, which does not mean, that the 50 m, can not be everything else. On the hike we go, Yet we keep the usual precautions. Minimum, what we can do for your safety, spacing is observed at a slope of 30 degrees, so not so.

Spacing at slope above 30 degrees should be at least 10 m (photographed someone to blame, tendency was not over 30 degrees, and met him at the direction of the photographer)

Norwegian probe
A similar technology as the moving block. The advantage is a faster version in two people, disadvantage difficult to evaluate, which requires significantly more experience, as well as finding stability only to the depth of bucket.

1) vyhloubíme hole with a width of approximately 0,8 m (three shovels) so that the snow profile is perpendicular to the slope
2) profile of snow cut off from the surrounding snow layer in the form of a truncated trapezoid, when its upper edge has a width of bucket (20 centimeters)
3) to the top of Keystone put a shovel and pull

Norwegian probe

Evaluation test
1) block is slid into loads of less 10 kg
2) block is slid under load 10 – 20 kg
3) block is slid in denial 20 kg or more

In the case of 1 not enter the hike and change the slope.
In the case of 2 continue the tour only with the greatest caution, in the case of a large group of target change, or renounce tours.
In the case of 3 slope can be considered safe. On the hike we go, But always we keep safety rules.