What you may have never heard before about avalanches, is written here …
AVALANCHE BULLETIN: the good and the bad…
Behind the preparation of the bulletins lies the work of hundreds of specialists. It has become a very popular tool, even among the media and the general public, and perhaps for this reason it is often misused. Here are some common problems.
a) The non-expert interprets the bulletin somewhat superficially. Danger rating 1 = exists only to start the ladder, rating 2 = you can go almost anywhere, rating 3 = it has snowed and the temperatures have risen a little, and therefore it is normal to give rating 3, but we go skiing anyway; rating 4 = uh-oh, we have to be careful …
Ultimately, only rating 4 raises your guard; however, according to statistics in the USA, 47% of fatal accidents occurred with degree of danger 3 (B.Temper, 2015).
b) Another situation: we start with rating 2 of the bulletin, but once on site we see small snow fractures from the base of the rocks. What is happening ? … It is never stressed enough that the avalanche bulletin gives only a very general situation, over a very large area that is hundreds of km2. But, as demonstrated by surveys carried out in various researches, on the same slope, the danger rating can vary by 1-2 and even 3 scores even at a distance of a few dozen meters, due to the micro-local weather conditions, the snowpack, and the terrain.
c) So who needs the bulletin and when ? For the non-expert, sofar it has been of little use, let’s admit it. Its interpretation is not simple in itself and, as seen above, must be integrated with the observation on the site.
For the expert, the bulletin is useful when visiting a new area, for which no recent field observations have been made.
d) The current bulletins already contain a lot of information, and are constantly evolving. However, they do not offer an historical situation of the evolution of the snowpack since the beginning of the season (in fact, that would be rather laborious). This, for the non-expert, changes little or nothing. For the expert, however, the lack of data on past evolution is a limitation when he/she wants to visit an area that is totally new to him/her.
e) The avalanche bulletin suffers from the errors in risk perception typical of any discrete index system, such as the classic risk matrix (D. Hubbard, 2009); additionally, the non-linearity of the scale make things even worse. As a consequence, an uncertain evaluation between rating 2 and 3, for example, can lead to too optimistic or, on the opposite, too conservative evaluations.
WIND EFFECTS: extremely quick and sometimes long lasting…
It is known that wind has a devastating effect on the quality of the snow and on the stability of the snowpack. But despite the bulletin info and expert advice, the effects of wind are often largely underestimated on a time scale. In fact:
a) Wind generates snow accumulations with speeds up to 10 times greater than a normal snowfall without wind (B.Temper, 2015). We all know that we have to be vigilant after a windy period, but few realize how fast the snow accumulation process can be.
b) The wind can generate highly cohesive plates that can remain compact but fragile for several weeks (risk of slabs). The problem is that, if these plates are covered with new snow, they are not visible. And, if we don’t know the local nivo-meteorological history, we don’t know their existence.
“I AM A FREERIDER: IF A SLAB COMES BEHIND, I ESCAPE ON A SIDE” … are you sure ?
It is a belief of many freeriders: if they feel the avalanche arriving behind while skiing, they slide like a missile down the slope, discarding sideways, and they save themselves... Most of the times this manoeuvre fails because the avalanche acquires high speeds in a few seconds, up to 150 km/h (B.Temper, 2015) in the case of powder snow avalanches. Only spring avalanches of wet snow are relatively “slow”.
SLOPE EXPOSURE: where is it (really) safer to go ?
Several publications show avalanche accident statistics based on slope exposure (north – east – south – west). In the Alps, according to some statistics, north-facing slopes see more accidents than all other exposures. According to other statistics, on the other hand, the slopes facing south-east are the ones that record the highest number of accidents. So let’s go west, is it safe ? No, all these considerations are of little value, since:
a) statistics are spoiled by external parameters, such as the seasonal weather evolution and the greater skiers’ attendance of the northern slopes at certain times of the year to look for powder snow;
b) causal factors are many and some may generate opposite effects – for example, in the south exposed slopes we may actually have more stabilized snowpack due to warming, but the heating of snow pack surface could generate wet snow avalanches; or as a second example, if there is a strong east wind, we could have important accumulations on the west sides and therefore a higher risk on that side;
c) data collected by statistics have a high dispersion around the average value, this indicates that the system is conditioned more from random variables than from easily identifiable causal factors.
Conclusions from all above: let’s look at the avalanche bulletin for a general idea also regarding the slope exposure, then use our mind to understand the evolution of the snowpack conditions and later observe the conditions on site. Forget the slope exposure statistics, which don’t really help here.
“I AM GOING WITH A MOUNTAIN GUIDE, SO I AM SAFE ” …true or not ?
Anyone who is not really an expert of winter mountaineering is well advised to get the assistance of a mountain guide. Local guides are often able to assess avalanche risk better than anyone else. However, a guide is not a lightning rod; even for a senior guide avalanches represent a complex phenomenon which is never under full control.
According to some statistics, more than one third of avalanche cases occurred in groups accompanied by a mountain guide. This does not mean that a guide is not providing a good level of safety, it only means that any guide can occasionally be wrong; sometimes the error is induced by the pressure of customers wishing to carry out that given itinerary at all costs, and by the business needs of the guide himself.
So what to do? Don’t hesitate to ask the guide about his/her assessments of risks, and what measures he/she intends to take. Ask which are the residual risks, that cannot be eliminated, and decide if you are willing to accept them.
FOLLOW A TRACK ? may be not a good idea…
“This is the track of a smart skier, let’s follow it, so we may also save some energy!” Common wisdom suggests to be careful when following a track in the snow, since we don’t know who made it. Why should we trust those we don’t know ? Yet, it happens also to experts to be influenced by the existing tracks, and follow them to unsafe areas.
COUNTER-BALANCING RISK FACTORS ? can be disastrous…
The human mind tends to simplify too much, and in so doing exposes itself to errors of logic (Dorner, 1989) and cognitive biases (Kahnemann, 1990).
Here is a scenario: we go out for a ski mountaineering tour, the temperature has risen, but on the other hand it has not being windy for at least three days, so any accumulations should have stabilized … The problem lies in the phrase “on the other hand” and now we explain why. The avalanche is a complex phenomenon where many causes generate multiple effects and all these variables are not independent, but correlated with each other, i.e. they have reciprocal effects. The temperature can contribute to an increased or decreased risk, depending on the correlations with the wind and on many other parameters that influence the final effect of the release of an avalanche. Now, even admitting to be able to quantitatively establish the negative effect of the temperature, as a variable theoretically independent, this cannot be counter-balanced for by the positive effect of lack of wind. In fact, the variables are not only correlated but are also probabilistic. And the sum of two probabilities is not the arithmetic sum of the underlying variables. With the probabilistic variables Bayes algebra applies and not standard arithmetics.
As a conclusion:
a) A low risk factor cannot compensate a high risk factor, giving a total average risk; therefore, either we are able to evaluate the effects of the two risks together, taking into account the correlations, or we proceed to decide on the basis of the higher risk (to stay on the safe side).
b) Some avalanche risk assessment tools, aiming at providing an overall risk index (such as the Munter reduction method or the Nivotest), being based on the aforementioned assumptions which are scientifically incorrect, may give completely misleading results. They can serve as a didactic tool, teaching how to take into consideration the various parameters, but not for a quantitative risk assessment..
c) In general, we suggest anyone who is not an expert in risk management and has not a solid background in probability and statistics, to avoid any attempt of quantitative risk assessment.
AVALANCHE SELF-RESCUE with beacon, probe, shovel: are we well trained ?
Everyone knows that it is essential to continuously practice search & rescue simulations. There are many courses made available for example by the mountaineering clubs and mountain guides. Furthermore, in the Alps there are several artificial fields made for the purpose of avalanche training.
The many tests carried out show disconcerting results on the possibilities of non-professionals to extract a buried subject within the time limit of 35 minutes (beyond which life expectancy is less than 30%). With the modern digital 3-antennas beacon, the non-professional can be able to locate the buried subject in less than a minute, but many minutes are then lost in the subsequent phases of probing and excavation.
However, the biggest problem often lies not in the technical phases of research with beacon, probing, and excavation, but in the management of the emergency: difficulty in electing a rescue leader (which is badly needed), inefficiency in establishing the roles and method of search (especially in the event of multiple burials), chaos with beacons on and off, uncertainty about the areas already cleared, doubts on the priorities to be followed, delays in communicating with the organized rescue service, panic, etc.
Conclusion: the training should include not only the technical phases of search & rescue, but also the management process, including the behavioral aspects of the people involved.
“WITH THE SMARTPHONE, I AM ALWAYS SAFE”…. or not ?
There are some smartphone apps on the market that allow you to make emergency calls to a rescue operations center, simultaneously sending your position in gps coordinates. That’s OK – so in the event of an avalanche, can we always count on help via smartphone? No, because in a mountain area the mobile phone network coverage is generally too low. The total coverage on the planet is obtained only with satellite phones (such as Iridium or Thuraya or, but with a very different function, emergency beacon transmitters such as the Spot or Garmin inReach).
Without forgetting that in any case and regretfully, organized rescue teams almost always arrive too late on site to extract alive a person buried in avalanche.
SAFETY DISTANCES : there is some confusion…
Some things said in the avalanche courses become so common and repetitive that no one dares to question them anymore. So, let’s take this case: we’re about too ski on a 35 ° slope with possible wind plates, we keep a safe distance between skiers of 20-30 meters, according to best practice…
But a slab avalanche rarely has a front less than 20-30 meters; slabs over 100 m wide are quite normal. Moreiver, if a distance of 30 meters is maintained between each skier, but then in the ascent zigzag you are on the same vertical path of a possible slab, what is the meaning of observing the distance ? Even a “small” avalanche with a 20m front could wipe out the whole group!
Why don’t we admit that a real “safe” distance should be at least 100 meters (horizontally!) Or, even better, we proceed one at a time to a safety island, and we wait for the companion to be totally out of the critical section before proceeding in our turn. It is true, doing so takes more time, but it should be done. Let’s not trust the classic 20-30 m safety distance rule.
THE “RED BULL EFFECT”…
Let’s describe the scenario: the shooting staff has little time, there is a short favorable weather window to film the descent, we get into the helicopters, and we go … Arriving on site in a rush often prevents an efficient risk assessment. You don’t have time to observe the mountain, and you decide under the pressure of haste and other factors. It happened to great athletes of international fame, who could anyhow count on an exceptional support in case of any emergency.
But coming to us, normal sportsmen without helicopters… let’s take the time necessary for a careful evaluation of the conditions of the mountain and, if in doubt, let’s ask for the support of a professional guide who knows well the local conditions.
EXCESS OF DETERMINATION
There are too frequent cases of avalanche accidents due to fixation on the objective, or excess of determination, or a mix of both.
It’s true that strong goal motivation underlies any success but, if the goal is to go for a tour to the mountains in the winter, we must not overdo the determination. In the past most mountaineering clubs and associations were used to set the calendar of the outings rigidly and many months in advance. Now they don’t do it anymore, it was understood that decisions about winter mountaineering must be based on the necessary flexibility. Even if we have been planning a route for a long time, once at the site, we shall carefully observe the conditions and, if they seem not favorable, we shall change the objective without hesitation or, in the worst situation, give up.