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Mountain safety - avalanche threat
Being
caught in an avalanche is perhaps the greatest fear of all those
who undertake off-piste skiing or boarding and ski-touring. The
boom in the snow sports industry, high lift-stations, fat skis
and snow boards have given access to the mountain to many who
do not have the necessary experience to deal with the conditions
and to recognise the warning signs. Snow conditions can vary from
day to day, and even hour to hour as weather conditions alter
the structure of the snow. Knowledge of the snow and understanding
of the terrain are necessary for the best form of avalanche safety:
that is avalanche avoidance.
The risk of avalanches on the patrolled runs is minimal as ski
resorts go to great lengths to protect their pistes - incidents
do happen but are thankfully infrequent. However, avalanches and
accidents can occur just off the pisted areas. The important point
is to be prepared before you venture away from the pistes. An
avalanche doesn't need to be of blockbuster movie proportions
to be extremely hazardous to your, or others', life.
A useful and daily updated avalanche risk guide
for the Courchevel and Three Vallees area is available from Henry's
Avalache Talk website. You can also catch Henry live
with a report about the day's off piste conditions on Radio Meribel
(97.9 Mhz or 98.9 Mhz) between 8am and 10am each morning.
The following information is not to be accepted as a set of instructions,
it is designed merely provide guidance for those who wish to go
off piste, and facilitating informed decision-making. It is also
worth noting that avalanches are not the only dangers of off-piste:
natural obstacles such as crevasses, buried rocks or cliffs are
also potential hazards. It is highly recommended that you take
a mountain guide whilst venturing into unknown territory.
• In 90% of avalanche incidents involving
skiers and snow boarders, the victim or someone in the victim's
party triggers the avalanche
• The common avalanches to occur are slab (which account
for almost all avalanche fatalities. A cohesive plate of snow
slides as a unit on top of weaker snow) or flow (powder) avalanches
• Experience indicates that about 90% of avalanche victims
will be recovered alive if they are pulled out within the first
15 minutes. After approximately 45 minutes, the chances of survival
drop dramatically to between 30-40%. After 2 hours, the chances
of being pulled alive are negligable
• Approximately 50% of victims, partially buried survive
if their airways are clear. Of the 50%, only about 5% will suffer
from deadly injuries due to the fall. Of the other 50% of victims
who die, death will usually be attributed to a late rescue as
carbon dioxide builds up in the snow around their mouths and
they suffocate
• The effects being caught in an avalanche potentially
include having clothing, rucksacks, and other equipment ripped
off the victim. Wearing a transceiver anywhere else but properly
secured around your body can increase the chances of it being
separated from you and therefore rendering it virtually useless.
Avalanche Terrain
Avalanches will most often start on slopes
of 30-45 degrees. However, that does not mean that avalanches
will not start on slopes as shallow as 25 degrees and as steep
as 50 degrees.
Knowing the slope angle is "rule number one" in recognizing
avalanche terrain, for once slope angles reach 30 degrees, it
is still potential avalanche terrain regardless of all other
factors. A clinometer and compass, to establish slope face direction,
are important tools for gauging slope aspect.
North-facing slopes are the most likely to avalanche during
the middle of winter. South-facing slopes become dangerous in
the spring and during sunny days as the sun begins to rise higher
in the sky. Leeward slopes – those that face away from
the prevailing wind; are dangerous because wind borne snow adds
to rapid accumulation of depth; also, the hard, hollow-sounding
wind slab may develop there. Windward slopes generally have
less snow and benefit from wind compaction.
Avalanche indicative risk or Hazard Rating numbers.
The avalanche risk off piste is classified from 1-5 and is intended
to give an overall indication only.
| Hazard Rating 1/5 - Low |

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Stability: The snow pack is generally well
bonded and stable
Activity: Triggering is possible only with high additional
loads[2] on a few very steep extreme slopes[4]. Only a
few small natural[6] avalanches (sluffs) possible |
| Hazard Rating 2/5 - Moderate |

|
Stability: The snow pack is moderately well bonded
on some[1] steep[3] slopes, otherwise generally well bonded.
Activity: Triggering is possible with high additional
loads[2], particularly on the steep[3] slopes indicated
in the bulletin. Large natural[6] avalanches not likely. |
| Hazard Rating 3/5 - Considerable |

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Stability: The snow pack is moderately to weakly bonded
on many[1] steep[3] slopes.
Activity: Triggering is possible, sometimes even with
low additional loads[2]. The bulletin may indicate many
slopes which are particularly affected. In certain conditions,
medium and occasionally large sized natural[6] avalanches
may occur. |
| Hazard Rating 4/5 - High |

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Stability: The snow pack is weakly bonded in most[1]
places.
Activity: Triggering is probable even with low additional
loads[2] on many steep[3] slopes. In some conditions,
frequent medium or large sized natural[6] avalanches are
likely. |
| Hazard Rating 5/5 - Very High |

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Stability: The snow pack is generally weakly bonded
and largely unstable.
Activity: Numerous large natural[6] avalanches are likely,
even on moderately steep terrain. Extensive safety measures
(closures and evacuation) are necessary. No off-piste
or back country skiing or travel should be undertaken. |
[1] Generally described in more detail in the
avalanche bulletin (e.g. altitude, slope aspect, type of terrain,
etc.)
[2] Additional load:-
High - e.g. group of skiers, piste machine, avalanche blasting.
Low - e.g. skier, walker
[3] Steep slopes: slopes with an incline of more than 30 degrees.
[4] Steep extreme slopes: those which are particularly unfavourable
in terms of the incline, terrain profile, proximity to ridge,
smoothness of underlying ground surface
[5] Aspect: compass bearing directly down the slope
[6] Natural: Without human assistance
Avalanche Survival
There is a lot of controversy about what to
do if caught in an avalanche. Some say swim (since a person
is about three times denser than moving avalanche debris) and
others say roll. The most important thing is to keep the mouth
free from snow especially when the snow comes to a stop. Try
and get your hands in front of your face to make an air space
as you are coming to a stop. An air-pocket is essential to survival.
Avalanche rescue - what to take with you when
off piste
For anyone going off marked pistes, (including
climbers, skiers, snow boarders, snowshoers and walkers); it
is advisable that the following items of equipment are carried
at all times:
Avalanche
Transceivers (beacons). Digital or analogue, these will send
out a signal of where the body is located under the snow and/or
assist in detecting the location of buried transceivers
Avalanche Probe. To localise a buried victim, and give exact
depth
Snow Shovel. For excavating the victim, quickly (speed is the
name of the game)
It is worth reiterating that none of these
devices will prevent an avalanche or prevent physical injury
from occurring, but will assist in the recovery process.
Before starting the day off piste:
• Take a course in avalanche awareness and practice
the techniques learned. Henry's Avalanche Talk is one such
way to find out more with regards avalanche safety and Mountain
Tracks run several such courses in alpine resorts throughout
the winter
• Look at the weather and avalanche forecasts for France
/ Switzerland, reviewing the degree of local avalanche risk
also.
Henry's
Avalanche Talk produces a translation of current
avalanche conditions in English and PisteHors.com is an excellent
reference also
• Don’t ignore advice given by local mountain
guides or others if advised to ski a certain path, or to keep
a specific distance between fellow members in a group
• Plan the route carefully, evaluating all different
options and assessing all elements of danger. Look at the
timings for each route. Inform others of your route, and when
you expect to arrive back
• Attach your transceiver properly to you and DON'T
FORGET to turn it on, test the signal is working, and make
sure you have all the necessary equipment. (A transceiver
is of no use if the user has not been trained in its use,
it is turned off, or it is in a rucksack - unless you want
just your bag to be recovered.)
Avalanche Transceivers
Avalanche transceivers work by sending / receiving electromagnetic
signals on a frequency of 457kHz. There are many transceivers
available in the marketplace using either analogue (older) or
digital technology. Digital and analogue transceivers are compatible.
Analogue transceivers working in "receive" mode, convert
the signals being transmitted by the "sending" transceiver
from underneath the snow into sound waves. The receive signal
is transmitted as a 'beep' which gets louder and stronger the
closer the receiving transceiver gets to the emitting transceiver.
Digital transceivers interpret the same signal. A microprocessor
converts the signals into visual data on screen, assisting with
more accurate directional information. Digital transceivers
are reportedly simpler to use than analogue ones.
Avalanche transceiver equipment tips
• Wear the transceiver as close as possible to your
body. A transceiver worn just below the waterproof layer will
be exposed if the layer is taken off when climbing and could
then be torn off by the force of the avalanche. In addition,
body heat will keep the transceiver and batteries warm aiding
battery life.
• It has been found that mobile phones interfere with
the electromagnetic fields of a transceiver, mobile phones
must be turned off at all times or in the very least kept
as far away from each other as possible
• Remove and dispose of batteries at the end of the
season. Use new batteries at the start of the season, test
and change frequently
• Train at the start of and several times during the
season, you can practice in your local park or even in the
back garden. The stress of an avalanche is not the time to
get the instruction book out! The search should almost be
reflexive
• Do not put a transceiver in your rucksack as this
may be torn off by the force of an avalanche, and will result
in only your rucksack being saved by the rescue services
• Probing at right angles on a steep slope reduces the
depth of snow to be dug (hypotenuse rule)
• Remember that the transceiver is just a search and
rescue device and doesn't enable you to go off-piste in poor
conditions
• Beginners often search with analogue devices at too
high a volume. The volume should be reduced systematically
to reduce the search area
• If not in Europe, make sure that the local frequency
is the same as that in use
• Remember an avalanche transceiver is the only device
that permits a group to perform their own search and rescue
operation in the minimum amount of time.
Some tips when skiing or boarding off piste.
• Ski or board one at a time. If there is a slope that
you are nervous about, only one person at a time should go
onto the slope. Whether crossing, or going up or down, do
so one at a time while all others act as spotters from a safe
location. Should an avalanche occur, there will be only one
victim and lots of rescuers
• Avoid the centre. The greatest danger on any steep
slope comes in the middle of it. Should an avalanche break,
there is no escape route. Avoid the centre of open slopes.
Cross it at the very top or bottom. Go up it or down along
the edges. These positions give a much better chance to escape
• Stay on shallow slopes. Generally, it is possible
to travel avalanche-free on slopes up to 25 degrees, and more
than 95% of the time it is safe on slopes up to 30 degrees.
To measure angles exactly, is it possible to purchase an inexpensive
slope meter. However; be extra cautious wherever steeper slopes
lie above shallow ones. Though avalanches won't start on shallow
slopes, it is possible that an avalanche could be triggered
above, placing individuals in harm's way
• Don’t travel alone. Whilst nothing may be as
companionable as one's self, there is no greater way to increase
an avalanche risk than traveling alone. There is no one to
save you from partial or shallow burials.
• Practice, practice, practice your avalanche drill.
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