Combining danger and terrain
“Avalanche risk”, “avalanche danger” … are terms that are still too often used as synonyms but they are separated from a fundamental difference. When we go out into the mountains in winter, it is difficult to control the danger of avalanches, but it is in our hands to manage the risk of avalanches, and in fact, it is the most important if we want to get home always alive!
How can we manage our own risk? By means of the risk equation, that we already have showed in a post of our Blog from a real case. Don’t be afraid, it is not complicated maths, if not a simple and basic formula, which, in addition to helping us to understand the great difference between the two concepts, helps us to see what we can do to mitigate our risk and that not only depends on the current avalanche danger.
The equation of risk:
RISK = HAZARD x EXPOSITION x VULNERABILITY
According to the equation, if we decide to enter into avalanche terrain, we decide to expose ourselves, and therefore there is always a certain level of risk, since there is not something 100% safe. But as the wise Canadian proverb reminds us, “If the snow is the problem, the terrain is the solution,” the key is to choose the adequate terrain for snow conditions to avoid the existing avalanche danger.
The AvaluatorTM Trip Planner is a Canadian tool that combines the snow conditions and avalanche danger (the avalanche danger rating) and the terrain severity (ATES class). It is a tool to help the user in the objective and systematic decision-making of the trip and that results in three categories of recommendations according to the level of training and experience of the group to travel safely in avalanche terrain.
These three levels of recommendations are represented in three colors in the matrix of the AvaluatorTM and are based on accident prevention values occurred and reported in the past in Canada.
– It is NOT RECOMMENDED to travel in the RED zone without professional or expert level knowledge on snow and avalanches. Conditions prepared for avalanche accidents.
– EXTRA CAUTION must be taken in the YELLOW area. Avalanche is possible due to human or natural causes, and accidents are frequent. An advanced level of understanding of the avalanche danger is required.
– In the GREEN area, the conditions are suitable for traveling in avalanche terrain and accidents are generally uncommon. You must have CAUTION, know how to recognize the danger and have safe travel skills and rescue.
According to Haegli and McCammon (2006), and from the analysis of Canadian cases, 75% and 36% of accidents could have been avoided if the people involved had limited their trips to the green or green and yellow zones combined, respectively.
In order to verify the functionality of the AvaluatorTM as a tool to help with the trip planning and the prevention values that it represent in our territory, we analyzed 160 incidents and avalanche incidents that occurred in the last 20 winters at the Val d’Aran and limit areas. We have combined the avalanche danger ratings on that day with the terrain class in the site of the accident or incident, and we have calculated the prevention values for our mountains. The following graph shows the results obtained:
– Limiting the trips to the green and yellow areas, and avoiding the red zone of the AvaluatorTM, 56% of accidents or incidents are avoided.
– Limiting the trips to the green area, and avoiding the yellow and red zones, we will be in 95% of prevention.
These prevention values are 20% higher than the Canadians, which means that the AvaluatorTM applied to the Pyrenees is more conservative and avoids a greater number of accidents.
This study was presented at the International Snow Science Workshop in Innsbruck (2018) under the title “ATES mapping and typical problems in avalanche accidents or close-calls in Val d’Aran, Central Pyrenees” and it can be read and downloaded here.
From the 2018-2019 season the ATES maps are available throughout the Val d’Aran which allows to apply the AvaluatorTM for all the planned trips in Val d’Aran.
Haegeli, P et al. The Avaluator – Canada Rule-Based Avalanche Decision Support Tool For Amateur Recreationists. ISSW, 2006, Telluride, CO.