W.A.R.T.S. and all (an article on Avalanche awareness as featured in OTE magazine)
Avalanches kill people every year and many of the victims trigger their own untimely demise. This is often due to the fact that they have little or no knowledge about the snowpack, or they ignore the very blatant signs around them that they are in the wrong place at the wrong time.
You don’t have to immediately start digging a snow profile every time you go out in winter. And even if you do then you have to be able to interpret your findings, realise the relevance of what you are doing, and extrapolate the results to other areas that you will be visiting later in the day. Tim Mosedale comes up with a chronological crib for you to remember what to take in to account about the snow and avalanche conditions when you are going out in to the winter hills.
The idea is that you progress through the various aspects as necessary and it may be that you don’t actually need to go to the trouble of digging a snow profile. Having said that this is not a snow profile avoidance scheme. If in the slightest bit of doubt then you should be conducting shear tests and looking closely at the snowpack.
But before you start digging have you carefully considered the following points?
W is for:
he Weather history. Prior to your visit to the hills you should try to follow the weather for a few days to build up a picture as to what may be happening to the snowpack. For instance if there is a thaw at all levels followed by a cracking good freeze and no winds then the chances are that the entire snowpack will be stable and that you will be able to travel safely in the mountains wherever you go. Perfect.
However when you are venturing out a few days later after there has been a fall of snow with little or no wind, the alarm bells should be ringing. In this case there may well have been a build up of surface hoar during the consistently cold period which has now been buried, forming the perfect sliding layer, that you could fail to notice if you were to dig a snow pit but that you would discover if you conducted a shear test (I’ll come to snow pack examination later).
The Weather report. As well as the recent weather history you should also have an idea what the forecast is for the day and how that may affect the stability of the snow. If there are winds forecast then where will the snow be redistributed and how does this affect your plans? It may be that your route is being scoured but don’t forget that your descent is possibly being loaded.
Have a look at Weather forecasts for further details
A is for:
Avalanche history. What has been happening in the last few days to the snowpack and its stability? Have certain slopes been continually reported as being unstable? Have avalanches been predominant on certain aspects of slope or at certain elevations? All this information is readily available on the phone or on the internet.
For further information check out Scottish Avalanche Information Service.
Avalanche report. The avalanche report is readily available for all the popular major mountaineering areas of Scotland (see websites above). It is an extremely useful way of keeping a track of what has been happening to the snow pack and what the experts think may happen on your day out. It should also be a determining factor as to whether you go West or East, whether you go to North facing corries or take the gondola up to East facing slopes on Aonach Mor. For the extra 20 minutes walk you can often have complete solitude and safety on Hell’s Lum or Stag Rocks whilst others have soft slab continually pouring down their routes in the Northern Corries. The avalanche report is not only available on the phone and internet but is also pinned up daily in the relevant car parks and access areas. You should read it. It is usually extremely accurate but remember that it is a forecast and is influenced by what the weather is doing It is still an inexact science and you should take the report and modify it throughout the day as you see signs around you and as the weather changes.
Aspect of slope. You have ascertained that the weather is to remain cold after a decent thaw, the avalanche report is category 2 and that windslab is expected to build on South facing slopes. If winds are from the North and your route and descent are both on North facing slopes, then you can travel in comparative safety for the whole day. But don’t drop your guard, be on the look out for any changes in wind direction or vortexes that may occur around the corrie that you are in and remember that there may be some crossloading on slope aspects to either side of your route.
Angle of slope. The classic range of angles for avalanches is from 25 to 45 degrees but that doesn’t mean that they won’t happen on other angles of slope. Whilst most of the routes that we climb are on ground far steeper than this what about the approach and, in particular, the easy angled slopes at the top of the route? Most people are aware of the notorious slopes above the routes at Meggie. What about the route that you are planning? It may well have a tiny exit slope but remember that it doesn’t take a whole load of snow to sweep you off your feet, which is a real bummer when you take a 300 footer down the route you have just climbed. Remember you can always retreat back down the route you have just climbed. You found sufficient belays to come up and you can therefore probably ab back down. So what if it costs a few pegs, wires and ab tat?
What is Above you? It may well be a perfect day at the end of the season and that you are walking and climbing on fantastic neve, safe in the knowledge that all the windslab has thawed and refrozen to the texture of reinforced concrete. But what about the fact that there is a very old, very slumped and very heavy cornice above you which will be getting a shed load of sun later on in the day?
R is for:
Route – where does it go? You may have ascertained that the approach slope is bomber and that you can safely get to the route, but what about the terrain that the route crosses? As an extreme example The Crab Crawl at Meggie crosses a whole range of different aspects and angles of slope, has a lot of potential for going on to cross loaded slopes and could have a range of dangers from above from cornices to heavily winbslabbed slopes. Remember also for all routes that you have to get off the top and on to the descent route.
T is for:
Terrain. Again where does your route take you? If there are boulders sticking out of the snow then these may be islands of safety … however be careful because they can also act as propogators for avalanches. Similarly there are notorious areas like The Great Slab in Lochain that are perfect sliding layers. Are there any terrain traps for the snow above you? You need to carefully consider not only whether there may be cornices or windslab above you but also whether there is the potential for crossloading throughout the day or for spindrift to come sloughing off down your route. On Point 5 Gully spindrift is sometimes but an exciting inconvenience. There are other days when the route will become downright dangerous, not only because you may be swept off your route, but also you have to question carefully what those top slopes will be like.
Temperature. Be aware of any significant changes in temperature throughout the day particularly sudden rises in temperature. This will usually result in decreased stability and is often a major avalanche warning sign.
Signs. The sorts of things that should be registering throughout the day are:
o raised footprints, sastrugi, drifts behind boulders or cairns, cornices and riming (all indicators that there has been wind and that snow has been redistributed)
o squeaky snow underfoot and areas of snow with a ‘chalky’ appearance (indicators of windslab)
o brilliant stars and reflections from the snow surface (surface hoar that is so light and feathery that it will form a perfect sliding layer if left in tact and covered with more snow later)
o cracks in the snow and slabs breaking off as you walk above the footpath (time to dig)
o sunballs, mud and dirt below crags and outcrops (has the temperature risen significantly?)
o avalanche debris etc etc.
There are even times when folk venture up climbs as avalanches pour down the routes to either side. Be aware of all the signs around you a keep adding to the overall picture.
The Snowpack. So the weather has been a little unsettled to say the least and the forecast is none too good. The avalanche category is 3 but you have wisely decided to go to ‘safe’ wind scoured slopes that you deem to be of the correct aspect. There are no terrain traps and your route is safe to access and exit BUT …
There is an oblique ridge downwind of you and it seems to be causing of a bit of cross loading on to your route. Sure enough whilst you are on a rising diagonal approach, walking on slightly squeaky snow, you notice that every time you walk above your partner’s footprints cracks appear in the snow and small slabs of snow shear off and leave a very flat surface exposed.
Well now is definitely the time to take a look at the snowpack. It’s all very well digging a ‘classic’ snow pit, getting out your credit card, prodding with your gloved fist, allocating various layers various numbers and ascertaining the profile of the snow but what does it all mean? Numbers are only of any use if you can interpret them.
A better method is to find out how easily the snowpack shears since this is what usually happens when it avalanches. The ‘walking Rutschblock’ is a good indicator of whether a 1 sq metre area of snow will fail catastrophically upon being loaded. To do this dig a front wall, with a vertical profile, down as far as the ground or the neve. You then isolate either side of the block and lastly the back wall (you can easily measure out 1 sq metre with your 50cm climbing tools). You then get on to the slope a few metres above, and off to one side, of the isolated block. Approach gently down the slope at 45 degrees until you arrive directly above the block. Gently sit down on the slope and place your feet on the top of the block. Push yourself ‘up’ in to a standing position (try not to just push the block, or yourself, down the slope). Next weight the block by flexing your knees downwards. Then comes a slight jump up followed by a full jump. You can then categorize as follows :-
|Fails during digging and isolation.
|Fails as you approach from above
|Fails as you get in to a standing position.
|Fails when you flex down.
|Fails with a small jump.
|Fails with a bigger jump.
|Does not fail.
You may well argue that we are all different weights and have different ideas about what is a small jump and a large jump but the important thing is that you are consistent with how you do the test. You will therefore build up a mental picture of what the conditions were like last time you came across a 2 or 3 or whatever. Even with individual discrepancies you are not going to be a million miles away from the results that other people come up with.
After this you will have a good idea if there are any shear planes within the snow pack and how readily they fail. Later in the day you can keep checking how that compares with what you are now stood on, and whether there are any inconsistencies for you check out further, by doing a smaller version of the Rutschblock. Simply kneel down in the snow and cut a front wall with your hands. Next cut out a semicircle above you and slide your hands behind the now isolated semicircle of snow. Trying not to apply any leverage see how easily the isolated block fails. This is not quite as easily to quantify as the walking Rutschblock because one person’s 4 will be another persons 5 but again the important thing is that you are consistent with your estimations. That way you will be able to compare today’s results with previous similar results and build up a valuable hard drive of memories.
Remember this is not the be all and end all of avalanche safety but is a checklist for you to follow to take everything in to account.
For further information I would recommend keeping the following books by the side of the loo :-
1) A chance in a million – Barton and Wright
2) Avalanche Safety for skiers and climbers – Tony Daffern
3) Snow Sense – Fredston and Fesler