ud 6-81-9 (e) a guide to cold weather operations, booklet 9, snow, avalanches and rescue (1998)

8/13/2019 UD 6-81-9 (E) a Guide to Cold Weather Operations, Booklet 9, Snow, Avalanches and Rescue (1998)

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UD 6-81-9A Guide to Cold Weather OperationsBooklet 9

Snow, Avalanchesand Rescue


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UD 6-81-9 E (english edition) A guide to Cold

Weather Operations booklet 9, "Snow,Avalanches and Rescue" has been issued for

use by allied wintercources and foreign unitsexercising under Norwegian command.

Terningmoen, november 1998

Jan Erik KarlsenBrigaderInspector of Infantry

Karsten ReitanLieutenant ColonelCommandant SVI


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UD 6-81 E

A Guide to Cold Weather Operations

includes:

UD 6-81-1 (Booklet 1): Winter conditionsUD 6-81-2 (Booklet 2): Personal ClothingUD 6-81-3 (Booklet 3): FoodUD 6-81-4 (Booklet 4): Frostbite and Other

InjuriesUD 6-81-5 (Booklet 5): MovementUD 6-81-6 (Booklet 6): Bivouacs

UD 6-81-7 (Booklet 7): Cold WeatherEquipment

UD 6-81-8 (Booklet 8): Field Works andCamouflage

UD 6-81-9 (Booklet 9): Snow, Avalanches andRescue

UD 6-81-10 (Booklet 10): Weapon effects


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Contents

Para PageForeword ................................................. 11

The theory of avalanchesIntroduction ............................................ 1 12Snow

Fresh snow .............................................. 3 13Metamorphism ....................................... 4 13Shapes of snow grains and crystals ..... 5 14Temperature ............................................ 7 16Avalanches

Types of avalanches .............................. 9 18Loose snow avalanches ........................ 10 18Flake avalanches.................................... 11 19Slush avalanches.................................... 12 19Forces working in an avalanche........... 13 19Avalanche movement ............................ 17 22The stability of the snow

Snow profile ........................................... 18 24Control of snow stability ...................... 19 25

Snow profile and the spade test . ........... 20 25The spade test......................................... 21 26The gliding block................................... 22 27The use of dynamite .............................. 23 28Weather causing avalanchesSnowfall and wind ................................. 25 29Rain ......................................................... 27 31Temperature ............................................ 28 31

Sunshine.................................................. 29 32Avalanche terrain

The avalanche area ................................ 30 33 The starting zone .................................. 32 33The avalanche track and therun-out zone ........................................... 33 34Shape of terrain ...................................... 33 35Frequency of avalanches indifferent terrain ...................................... 35 38


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Para Page

The range of an avalanche.................... 36 39Methods for measuring the range

of an avalanche ...................................... 36 40The effect of avalanches on forests

and loose masses

Forest ....................................................... 38 41Loose masses .......................................... 41 42

Preparations and training interrain prone to avalanches

Preparations

Map ......................................................... 42 44Avalanche map ...................................... 45 45The avalanche maps divisioninto zones ................................................ 46 47Zone I ..................................................... 47 47Zone II..................................................... 48 47Limitations of the avalanche map ........ 49 47

How to use the avalanche map ............ 50 48

How to operate in avalancheprone terrain

General .................................................... 52 50Weather report........................................ 53 51Precipitation ............................................ 55 51

Wind ........................................................ 56 51Temperature ............................................ 57 52Snow........................................................ 58 52Ground .................................................... 59 52Changes in weather ............................... 60 53Choosing a safe route ............................ 61 54Crossing dangerous ground.................. 62 54


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The avalanche group

Para PageGeneral .................................................... 63 56Organization ........................................... 64 56

Task and responsibility.......................... 66 58Equipment and materials....................... 69 59Communications equipment ................. 70 59Spades ..................................................... 71 60Transponders .......................................... 72 60Vehicle and trailer .................................. 73 60Helicopter ............................................... 74 60Thermometer, screen,

snow profile forms ................................. 75 60PC with modem...................................... 76 60Bivouacking material and provisions .. 77 61

Rescue

General .................................................... 78 62Helping yourself .................................... 80 62Quick search ........................................... 82 63

Primary area of search........................... 84 64Avalanche guard .................................... 85 65Surface search ........................................ 87 66Tentative search ..................................... 88 67Warning................................................... 91 69Digging out and treatment of casualties95 70Planned search in an avalanche

Responsibility......................................... 96 72

Organization and tasks .......................... 99 73Personnel and tasks ............................... 103 74Rescue leader ......................................... 105 76Branch leader avalanche ....................... 106 76Operational medical leader ................... 111 78Branch leader medical ........................... 112 78Branch leader order ............................... 114 78Log keeper/intelligence officer ............ 115 79Communications officer ........................ 116 79


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Appendix

Page

Interpretation of snow profile form ....... 104-107

Gliding block ........................................... 108-110Measuring the angle of inclination ........ 111Estimating the range of an avalanche.... 112Avalanche warning .................................. 113-114Rescue kit, primarily for avalanches ..... 115-117HF 5-2 ....................................................... 118-121How to move where there is avalanchehazard in special situations ..................... 122-125

The vital avalanche rules ........................ 126Litterature.................................................. 127


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Figures

Page

Fig 1 Destructive metamorphism .............. 14

Figure 2-3 Forming of ice bridgesbetween snow crystals ...................... 15

Figure 4 Growing metamorphism................... 16Figure 5 Classifications of avalanches ........... 18Figure 6 Snow can take stretch, stress and

shearing forces .................................. 20Figure 7 Forces influencing a snow flake

on a slope ........................................... 21

Figure 8 Examples of fractures or breaks in thesnow layers ........................................ 22

Figure 9 Pit for a snow profile......................... 24Figure 10 The spade test .................................... 27Figure 11 Use of dynamite ................................ 28Figure 12 The snow make the terrain look

steeper than it relly is ........................ 35Figure 13 Release area at bottom...................... 36Figure 14 Release area in gap ........................... 36

Figure 15 Release area in open concave terrain36Figure 16 Lssneomrde i konvekse partier .... 36Figure 17 Avalanche prone terrain which

not can be seen from bottom ofthe valley ............................................ 38

Figure 18 Simple method for estimatingrange of an avalanche....................... 40

Figure 19 Trees that have often been

exposed to avalanches ...................... 43Figure 20 Forest hit by an avalanche................ 43Figure 21 Stone wall deposited by an

avalanche ending in a river .............. 43Figure 22 Avalanche map with suggested

probability of route ........................... 46Figure 23 Weather data in a meteogram........... 50Figure 24 Flake avalanche in narrow valley .... 53Figure 25 Follow ridges - be safe...................... 54


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Page

Figure 26 The table of organization for fieldexercises of 2 brigades

or equivalent ...................................... 57Figure 27 Deathrate in avalanches.................... 63Figure 28 Choise of primary area of search ..... 64Figure 29 Tentative search ................................. 66Figure 30 Digging out casualty ......................... 70Figure 31 Table of organization for

rescue leader ...................................... 71Figure 32 Organization of accident area .......... 75

Figure 33 Systematic search .............................. 84

Figure 34 Search pole ......................................... 89Figure 35 Avalanche rope.................................. 91Figure 36 Transponder ....................................... 91Figure 37 How to use the transponder before . 92Figure 38 How to find a person caught by ...... 92Figure 39 How to carry a transponder.............. 93Figure 40 Detector with search unit,

headset and power element .............. 94Figure 41 Placing of the reflector into the field

trouser and the field jacket ............... 96Figure 42 Placing of the reflector on the boots 96Figure 43 Search with detector .......................... 96Figure 44 Cave for person posing as casualty 101


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Foreword

This booklet has been made by the School of

Infantry and Winter Warfare, the NorwegianInstitute of Geotechnology in cooperation with the

Norwegian Red Cross rescue team. In addition

Norges Hgfjellskole has contributed to the

chapter dealing with search and rescue.

The purpose of this booklet is to increase the

officers understanding and knowledge of how to

choose a safe route to avoid being exposed to an

avalanche. The booklet is also meant to enhanceofficers theoretical knowledge of avalanches and

search and rescue operations.

Yet it has to be added that a complete understand-

ing of this topic can only be achieved through

continuous practice and training.

The booklet is aimed at those officers who have

acquired practical experience and applies in

particular to instructors made responsible for

arctic training within their units, staff officersresponsible for the planning of winter exercises

and members of the avalanche team.


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The theory ofavalanches

Introduction1. In order to train our units to execute all types of

winter operations, all kinds of winter conditionsincluding how to operate in mountain areas mustbe mastered.Our urbanised way of life has made us accept quitereadily a number of safety measures, like for

instance the car safety belt. In leisure time,however, it looks as if neither research,warnings or strict measures taken by profess-ionals related to avalanche hazard carry anyweight. It is therefore a public duty for theMilitary to train our soldiers for winterconditions and to give them understanding ofthe importance of choosing a safe route.In case of an accident they should also be able toparticipate actively in search and rescue operations.

2. About six people are killed yearly by avalanches inNorway. Over the past years the number of skierskilled in avalanches has been increasing.If totally buried by an avalanche the possibility ofsurvival decreases as time passes, and after aboutthree hours, usually only one in ten will be alive.

To prevent future accidents, it is important toimprove the knowledge of the factors whichcontribute to a potential avalanche.The three factors are:

The snow The weather The terrain

The first part of this booklet covers these threefactors, one by one. Then the interplay and the


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importance of the different factors will becovered.It must, however, be emphasized that in this field,more than in many others, it is absolutely essential

to use a practical approach. Science has come faralso in this field, but there are no research findingsthat can guarantee a safe choice of route. Thetheoretical basis must be supplied with practicalexperience in evaluating snow, weather and terrain.

Snow

Fresh snow3. Snow is solid water. Sometimes snow falls in the

shape of hexagonal stars. For the snow stars to falldown in one piece it has to be calm or very lightbreeze. For elaborately shaped fluffy snow crystalsto fall there also have to be clouds and an equallylong time of fall, a few degrees below zero and dryair. In damp air, rime will cling to the crystalsmaking them lumpy and white. Usually snow fallsin the shape of needles or simple star-shapedforms.The new snow crystals can be destroyed by thewind even on their way to the ground or by thewind causing the crystals to blow along the surface.New snow fallen in calm and cold weather,often called loose snow, is light and fluffy.There is little binding and consistency in such

snow and loose snow avalanches may betriggered if the terrain is steep enough, i esteeper than 30O and up to 60O. If it is steeperthan 60O the snow normally falls down intomany small slides.

Metamorphism

4. The snow crystals which consist of a number ofspikes with sharp edges, have little stability.


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A destructive metamorphism in the snowcrystals start immediately, which means that theedges and spikes are being destroyed becauseof sublimation, see fig 1.

Shapes of snow grains and crystals5. Shapes of snow grains and crystals. If each layer

of snow is carefully examined it does not take longto establish that the layers consist of fine grainedsnow. There is a connection between wind polish-ing, wind packing and the binding of the snow.There is probably one or several layers of snowcrust. Rough grained snow common in late winter

(Easter) or in snow patches found during summerin the mountains can be formed.The layer closest to the ground often becomesrather loose during winter, depending on how coldit has been.Most often there are edged snow grains where theedges are straight and characteristic 120anglesindicate crystallizing. When this process is allowedto go on unchecked the eventual outcome is

Figure 1Destructive meta-morphism.


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hexa-gonal pyramids with strips parallel withthe sides of the base. Because pyramids usuallyare hollow the term cup crystal is used. More tothe point is probably the Norwegian term

sliding snow (rennsn) (because of much airand little binding in such layers).

6. In winter and especially in a coastal climate acrystalline relation of the sliding snow is more rareand appears as thin glittering strips between finegrained layers. The typical 120angles andparallel strips with sides of the base are recognized.

Such surface rime, however, consists of thin slateswhich are extremely slippery. In winter andespecially in a coastal climate thin layers of hailmay be observed. A close scrutiny will reveal theircolour to be whiter than summer hail. The smallballs are also porous and quite aptly called brittlehail. This has a bearing on the release of flakeavalanches. Figure 2 and 3

Forming of icebridges betweensnow crystals.


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Temperature

7. The temperature on the ground under the snow isnormally close to 0C because of the heat fromthe earths interior. The surface of the snow,

however, will adapt to the air temperatureespecially in clear weather with little wind.If there is a thin snow layer combined with alow air temperature the difference intemperatures between the top and the bottom ofthe snow will be large. The relatively warmsnow near the ground contains more water thanthe colder snow near the surface, and

consequently there is a movement of watervapour upwards the snow. This vapour will besublimed on the snow crystals in the upperlayers. The results is that a growingmetamorphism starts and the crystals formplane slates. At first the crystals form shapeslike cubes or prisms (grained snow), and if theprocess goes on long enough, hexagonal,hollow crystals, so-called cup crystals will

develop (fig 4).

Figure 4Growing meta-morphism


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8. Crystals which grow in this way can be severalmillimetres across and the contacting surfacesbetween the crystals will be reduced. Theconsequence of this is that the cohesion between

the crystals will also be reduced.After a long period of cold and little snow a greatdeal of the snow will be transformed into cupcrystals, or so-called sliding snow. This snow haslittle resistance and will start sliding at the lightesttouch. It is common that such layers are formedduring the winter and they will first appear near theground. This layer can withstand the weight of

new snowfalls while a sudden weight of, forexample a skier moving in the area or a cornicefalling down, may be enough to cause fracturesin the snow. Thundering sounds in the snoware often a warning sign to skiers in the area.


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AvalanchesTypes of avalanches

9. Avalanches can be divided into two main groups:- loose snow avalanches- flake avalanches.

Loose snow avalanches

10 Loose snow avalanches occur normally on thesurface of the snow when the binding between thesnow crystals is weak. This is the case with lightnew snow recently in calm weather or fallen in

spring when sun and rain melt the binding betweenthe snow grains.Loose snow avalanches often start at a point andspread out in a pear-shaped form.

Figure 5Classifications ofavalanches.


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Flake avalanches

11. Flake avalanches are characterized by a firm layerof snow gliding on a looser layer further down inthe snow or along the ground. A sharp breaking

point along the upper end is formed. Flakeavalanches can contain great masses of snow whenhillsides several hundred metres long can break atthe same time. The breaking points height can beseveral metres high. The flake will be broken upinto small snow blocks in its path. When theavalanche reaches the bottom of the valley it maytherefore be difficult to decide whether the

avalanche was set off as a flake or loose snowavalanche. Even though the snow is light andloose at the bottom of the valley there is a dangerthat a flake avalanche may start higher up in themountain side where the terrain is more exposed towind.

Slush avalanches

12. Slush avalanches can occur after heavy rain and

snow melting. It is vital to stay out of courses ofbrooks or in large brooks running down to thebottom of the valley. This type of avalanchescan be released at places with an angle ofdeclination less than 30 and may have a rangebeyond the 20angle rule.

Forces working in an avalanche

13. To understand the triggering mechanism it isnecessary to take a closer look at the forcesworking in a snow layer. Depending on time,temperature and humidity a metamorphism ofthe snow grains will occur which causes greatercompactness. This process can be observed asa compression in the snow as the depth of thesnow decreases.


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On a slope the snow grains will move partlyalong the plumb line because they set, but theforce of gravity will in addition lead to aparallel movement with the angle of

inclination. The greatest movement occurs onmountain sides. Moreover, the snow may glideon the underlying layer if this is smooth, like eg a slope of naked rock or grassy field. Theconsequenses of movement and gliding can beobserved because trees on steep, snow richslopes get a characteristic bend from the root upto a certain point on the trunk.

14. Because the terrain varies both in roughnessand angle of inclination, the movement of thesnow grains will vary in speed from one placeto another. This causes tension in the snow.The force of gravity influences the snow flakeon a slope. To keep the snow in place, thisforce has to be absorbed along the sides andbottom of the flake. We must distinguish

Figure 6Snow can take stretch,stress and shearingforces.


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between shearing, stretching and stressingforces. Fig 9 illustrates how these forces workin a snow flake on a slope.

Figure 7Forces influencing asnow flake on aslope.

15. The abilityof the snowflake to with-stand differentforces dependson the snowsshearing, stretchingand stressing com-pactness. If the strain

becomes too strong theanchors will not hold andan avalanche will be set off.The shearing forces are of vitalimportance in setting off an avalanche becausethey influence the weak and loose layers furtherdown in the snow. Also quick accumulation ofsnow either by snowfall or through drifting may

cause breaks in loose layers. The break can beheard as a thundering sound when the snowsinks. The consequence of this, is that the flakeloses its anchorage and an avalanche can betriggered (figure 10).

16. Most accidents involving skiers occur because theskier sets off the avalanche as opposed toavalanches being triggered by natural causes.


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In periodes of unstable conditions a break in thesnow at the foot of a hill can spred very quicklyup the slope and cause flake avalanches to bereleased higher up on the mountain side.

Never move close to the foot of a steep hillwhen thundering sounds can be heard from thesnow.51.

Avalanche movement

17. When an avalanche moves down a mountain sideits speed increases rapidly. Its movement is at first

a glide because the snow flakes are broken up intosmall blocks which glide on a plane surface. Asthe speed increases the blocks are brokendown and the avalanches becomesa mixture of snow whirled up into the air(snow cloud) and snow balls rolling, jumping

Figure 8Examples of fracturesor breaks in thesnow layers.


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and sliding on the surface. The greatest speed adry flake avalanche can reach varies usuallybetween 30 and 60 m/sec (about 100-200 km/h)depending on angle of inclination and the

consistency of the snow. Avalanches of wetsnow can have greater friction and the speed isreduced to 10 to 30 m/sec about 35-100 km/h.The snow masses will harden when theavalanche has come to a halt and the snowbecomes hard and fast. It is difficult to dig inthis snow and in rescue operations steel spadeshave to be used. The accumulation of snow in

an avalanche may be more than 10 m deep ifthe avalanche stops in narrow passes. In flatterrain the accumulation of snow will be muchthinner. If the snow is wet the masses have atendency to form concentrated tongues orcones.


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The stability of the snowSnow profile

18. Depending on how late it is in winter and how theweather has been, the snow is more or lessdeposited in layers. In bad light the layers arehard to observe. However, it can be noticed thatthe resistance varies with the layers of theprofile. For a simple comparison of the theresistance there is international agreement onusing the hand test. This method is described inannex 1.It is also possible to establish the layers by

sweeping the profile with a mitten, a brush etc.. Ifthe light is so good that each layer can be observed,or the differences can be established by using hand,pencil or knife, there is no doubt that the snow onsteep leeward mountain slopes is deposited inlayers

Figure 9Pit for snow profile


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Control of snow stability

19. Snow stability can be controlled as follows: Snow profile and spade test Gliding block

Dynamite

Snow profile and the spade test

20. Fore more than 20 years the use of the snow profileand the spade test as means to develop a betterunderstanding of the snow and why avalanchesare released have been developed in Norway.

The method is aiming at creating familiaritywith the snow when moving outdoors andfinding spots where the method can be applied.While moving variations in the snow layer canbe observed. Varying resistance will decide ifskis can carry a person on top of the snow or ifhe sinks into the new snow and the skiingconditions will change with grain and crystalforms. The depth of the snow will vary with

vegetation and the shape of the terrain in diffe-rent areas. After a period of wind, ridges andhills may be swept bare of snow above the treeline, while on the leeward side great masses ofsnow may have been accumulated. In asheltered wooded area the new snow may lieuntouched and offer an opportunity for study-ing each hexagonal snow crystal.

In order to find out how avalanches are formed asnow profile dug above the tree line on leewardslopes compared to the dominant wind directionwill offer the best information. The term snowprofile means a cut through the entire snowlayer. The cut is to be dug vertically to thewind direction and the difference in height onthe leeward slope is not to exceed 5 metres -danger of avalanche! The height of the snow


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should be more than 1 metre so that all layersare included (a search pole can be useful). Thesteepness of the leeward slope shouldpreferably be around 30 or steeper. Dig the

profile 3/4 metre wide and smooth the surfaceof the cut using the spade.

In order to check the stability of the snow and ifavalanches can be released, the best method isto dig a snow profile above the tree line on

leeward slopes compared to the dominant wind

direction. ....When the snow profile has been studied it is time

for the spade test to establish how great the dangerof an avalanche is. Several gliding layers in thesnow profile are often found which were notapparent in the study of the profile.Experience shows, however, that all layersinfluencing on the danger of an avalanche arerarely found through just the spade test.

The spade test21. The approach is to cut a trapezoid-shaped piece

from the upmost layer in the same way a cake iscut, with the width of a spade. With the spade ina vertical position, try to loosen layer by layer.The binding between the layers is more or lesssolid which becomes evident as it is dug downthrough the layers.

The spade test makes clear experiences which arenormally not put into context. It shows that finegrained snow makes flakes (with a resistance offour fingers or more solid). It also proves thatthe anchoring between the single flake of finegrained snow and underlying layers is weak. Itmeans that in places where the flakes are thickenough, i e heavy enough compared to thebinding beneath and the steepness of a leeward


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slope with sufficient level of height a flakeavalanche may be released.A flake avalanche is the very type of avalanche towhich skiers and band wagons are most exposed.

In winters with little snow, it may be tempting tocross where there is a lot of snow, where the windhas deposited snow in the shape of fine grainedflakes on the leeward slopes.

The gliding block

22. The gliding block is a more time consuming

method than the spade test. See appendix 2.

Figure 10The spade test


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Figure 11Use of dynamite

The use of dynamite

23. This gives a very good indication whether an

avalanche can be released. This method isnormally reserved for the avalanche team.Dynamite can be used like this:

a. 1-3 kg charges placed on top of the snow orpreferably 1-2 m above the snow and close to aloose area

b. 5-10 kg charges lowered from helicoptersc. 20-25 kg placed on bare rock so that the

reverberation will release an avalanche. To be

placed as close as possible to a loose snow aread. 20-30 kg dug down into a crested snow drift.

When the snow drift falls down it may release anavalanche.


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Weather causing avalanches

24. Snowfall and wind Rain Sunshine

Snowfall and wind

25. Most avalanches are released during or shortlyafter heavy precipitation when the large lowpressure areas move across the country. They areoften followed by showers which can cause heavy

precipitation along the coast and the mountainswest of the watershed. As described in para 2, theability of air to hold vapour is dependent ontemperature, i e cold air can contain less vapourthan hot air. The temperature decreases usually at6-7C per 100 metre rise. When damp air from thesea around Norway moved towards land, the air ispressed upwards and the temperature falls. The airtherefore cannot contain so much vapour and thereare clouds and precipitation which means that theheaviest precipitation will fall in the mountainssome miles from the coast. After the mountainshave been passed, the air will sink again and theprecipitation decreases. As a rule the amount ofprecipitation increases with the height above sealevel.

It is hard to give guidelines about when anavalanche can be set off. In addition toprecipitation, wind and the angle of inclination areimportant. How well the different snow layers arebound together must also be taken intoconsideration. An avalanche may occur whennewly fallen snow reaches a depth of 20-30 cm ona surface offering bad anchorage.


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In cases of heavy snow fall, 50 cm or moreduring 24 hours, the conditions may becomeunstable and if the terrain has the right form anavalanche will probably be released. If the

snowfall lasts for some time, the snow will sinkand more snow is needed before the risk of anavalanche becomes equal to a situation withheavy snowfall over a short period of time. Theintensity of the snowfall will consequently be ofimportance in assessing the risk of anavalanche, is shown in figure 11.At wind speeds above 5 m/sec the degree of danger

on leeward sides must be increased by a factor of 1or 2 depending on the speed and the duration of thewind. The figure applies to the danger of anavalanche in a large area.

26. The estimation of the danger of an avalanchevaries from time to time. In some cases only 20cm of newly fallen snow is enough to set off anavalanche, in other cases it takes more than 100

cm. After periods of snow fall and wind thedanger of naturally released avalanches willsoon be over, but the danger still exists forrelease through human activity.Not only the amount of newly fallen snowinfluences the danger of avalanche, wind is also ofgreat importance. A heavy snowfall is needed toset off an avalanche in calm weather as opposed to

when a wind is blowing.In windy weather much of the snow will blowaway when the wind direction is towards amountain side. The snow will be accumulated onthe leeward side or where the wind is too weak tomove the snow, i e where the wind speed isbelow that of a fresh breeze. Areas to theleeward side will therefore accumulate greatermasses of snow even if the precipitation is


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moderate. Furthermore, the wind causes thesnow crystals to break into pieces and theiredges are polished, packing the snow densely.It has the ability to withstand greater strain then

loose snow and great masses are allowed tobuild up before an avalanche is set off.

Most avalanches occur on leeward slopes wheregreat masses of snow have been accumulatedthrough precipitation and wind.51.

Rain

27. It is not only snowfall which will triggeravalanches. Rain following snow will soften snowand the resistance of the snow is decreased. It isassumed that 5-10 mm of precipitation per day canbe enough to set off an avalanche. The structure ofthe snow is important because rain following newlyfallen snow is liable to release avalanches muchmore quickly than rain falling on old snow.

Temperature

28. Temperature is of importance for the stability of thesnow. When the temperature rises, thecompactness is diminished so that the risk of anavalanche increases at first. Then the snowbecomes gradually stabilized by the mild

weather, because the destructive metamorphismand the forming of ice bridges between thesnow grains accelerate so that the compactnessimproves. At low temperature the destructivemetamorphism of the snow crystals and theforming of ice bridges are slow, and the snowmay be unstable for several days after asnowfall.Over a long period of time (several weeks) the


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temperature is important in the relatively thinsnow will turn the lower layers into glidingsnow which makes the snow more unstableduring a cold period.

Sunshine

29. In spring, as the sunshine becomes more intense, itwill have a warming effect on the snow. Howmuch solar energy is accumulated in the surfaceof the snow, depends on the consistency of thesnow. Newly fallen snow which is not too

polluted from industrial effluent, will reflect upto 90% of the sun rays. Older snow will reflectconsiderably less so that it warms more quicklyand becomes moist. The moisture willpenetrate the snow downwards and theconditions will be similar to the effects of rain.This can occur even if the air temperature isbelow 0 C. Intense sunshine in spring thusincreases the danger of avalanches.


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Avalanche terrainThe avalanche area

30. The avalanche area is divided into:- starting zone- avalanche track- run-out zone

31. Concerning small avalanches, there is littledifference between points a and c. Bigavalanches spanning the larger part of amountain side, may cover a long stretch ofterrain between the release area and the

avalanche cone.

. The starting zone

32. The inclination or the steepness is the factor whichis of the greatest importance concerningavalanches. All slopes between 30 and 60

can cause avalanches if rocks and otherobstacles are covered by snow.Flake avalanches, considered to be the mostdangerous ones, are rarely set off when theinclination of the sliding layer is less than 30.In very steep terrain the snow will not beanchored and therefore slide gradually.Terrain steeper than about 60 will not causeavalanches.When the angle of inclination is down towards 30

relatively large amount of snow is needed to set offthe avalanche because the anchoring forces areusually strong enough to hold the snow. At asteepness of 50- 60less snow is required for anavalanche to be released. Avalanches are thereforemore frequent, but smaller.Because the snow is deposited unevenly on a slopethe critical angle of inclination causing the releaseof an avalanche can be exeeded. Research carried


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out in this country on about 500 largeavalanches shows that most of them are relea-sed at an angle between 35- 50 . Thisresearch covers self-triggered avalanches, i e

due to weather conditions or because ofchanges in the stability of the snow.Measurements taken of a number of avalanchesreleased by skiers show that the lower releaselimit of flake avalanches is about 30.

The avalanche track and therun-out zone

33. Avalanches will follow the hollows of the groundand all the time seek the lowest points or wherethere is little or nothing to stop them. Markedfeatures like ridges and hills decide their course. Ifthe snow is dry and the avalanche moves at greatspeed the snow masses may still pass 25-30 metre-high hills. The greater the speed and volume of theavalanche, the greater its capacity to move forward

in a straight line i e in the direction the mountainside slopes.When the angle of inclination is down to about 15-20m , the breaking of a dry avalanche normallystarts. Large dry avalanches can move over flatground and cross bottoms of valleys spanningseveral hundred metres unless they are stopped in,or not far from, the slope where they were relea-

sed.This is also the case when the snow is moist or wetbecause of the great friction in the snow. Anexception is so-called brush or slush avalancheswhich contain so much water that they run likerivers.

To determine how steep a slope is, the followingtwo methods can be applied:


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- use of ski poles- use of compass and water bottle

These methods are described in appendix 3.

Shape of terrain

34. In addition to the angle of inclination the shape ofthe terrain itself is of great importance as to wherean avalanche is set off on a mountain side. Areas

on the leeward side are usually most avalancheprone. A lot of snow is accumulated here and therisk of an avalanche increases with the amount ofsnow. Consequently the risk of avalanches isgreater in hollow and bowl shaped terrain (concaveterrain) than on hills and mountain ridges wherethe snow normally blows off. The most commonleward areas of a mountain side are small gullies

and passes of varying shapes, crevices and markedgaps. Bottoms, i e areas where there is orpreviously has been a glacier, are also typicalrelease areas for large avalanches (see figures 14-16). Where there is a marked transition from aprecipice to a more gently slanted area below, forinstance an area of scree, large masses of snowmay accumulate. Slopes of naked rock and evengrassy surfaces may often cause avalanches,

Figure 12The snow make theterrain look steeperthan it really is.

Notice, however,that the angle ofinclinationestimated byusing a map can

be wrong in theterrain becauseof theaccumulation ofsnow.


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especially late in winter

when sunshine and rainmake the snow thoroughlywet so that melted water atground level reducesfriction. Where thesteepness of the terrainincreases downward(convex areas) stretch

tension is inherent in thesnow. This is also the casejust below areas where thesnow layer is well anchoredto large stones and outcroprock. In such stretch zonesavalanches are easilytriggered.

Figure 13Release area atbottom.

Figure 14

Release aarea in gap.


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Figure 15Release area inopen concaveterrain.

Figure 16Release area inconvex terrain.


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Frequency of avalanches in differentterrain

35. According to an investigation of about 250avalanches on the west coast of Norway, the

shape of the terrain in the release areas ofavalanches is as follows in order of frequency:

Shape of terrain Distribution in percentageof avalanche frequency

1. Open concave slopes and gaps. 292. Deep passes, crevices. 27

3. Convex areas. 124. Slopes of naked rock. 125. Bottoms. 106. Below zones of anchorage. 10

As the survey shows, about 60% of allavalanches from bottoms, deep passes, crevicesand concave slopes are set off where the wind

does not get a hold. Large avalanches probablyalso come from such areas. On the other hand,we must watch protruding ridges and hills ifthey are covered with snow because avalanchescan also be released here, especially duringsnowfall and little wind.If a mountain has a flat top, much snow can beswept down the leeward side of the mountain. The

risk of an avalanche on such a mountain side isgreater than when the mountain top is shaped like asharp ridge.The height of a slope need not be great beforean avalanche may pose a serious threat. Thereare cases in which skiers have been killed onslopes only between 5 and 10 metres high.Most fatal accidents occur on slopes between20 - 40 metres high.


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Angle (A) (range) Frequency of avalanche

20 or less 2 %21 - 25 12 %26- 30 24 %31- 35 27 %

36- 40 22 %Above 41 13 %

Usually the angle A is a little above 30. Inrelatively gentle tracks with an even transition tothe bottom of the valley, this angle may bereduced to 19-20 . A method of measuringthe range of an avalanche is described in ap-pendix 4.

Figure 17Avalanche prone terrain whichnot can be seen from thebottom of the valley.

The range of an avalanche

36. The table below shows how the range in degrees

(angle A) is distributed in relation to the frequ-ency of avalanches.


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Methods for measuring the range ofan avalanche

37. b. This method starts with the horizontal distancefrom the release area. It is called the 20 degree

rule. This means that when the sighting linefrom our position at the bottom of the valley tothe potential release point is 20 , the avalanchewill only occasionally reach so far. To be on thesafe side, the sighting line should make anangle of 20 or less, at ratio 1:3, see fig 20.Figure 18

Simple method forestimating range ofan avalanche.


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The effect of avalanches on forestsand loose masses

Forest

38. When trees are hit by avalanches, they aredamaged in various ways. Such damage can beused in considering the danger of an avalanche, orhow frequently an avalanche is set off. Even if theforest is quite dense on the mountain side, this isno guarantee that it is a safe area, but it proves atleast that avalanches are relatively rare.If a large avalanche is set off above the tree line,

and the mountain side rises 50 - 100 m above theforest, the avalanche will have sufficient speed topass through the forest. The reason for this is thatthe avalanche only needs a short distance before itsspeed is so high that the trees cannot withstand itspressure.

39. Where there are annual avalanches there is noforest. In areas where avalanches are less frequent,

the trees are small and their trunks are bent becausethey are often pressed to the ground, see fig 21.Notice that such damage may also be due to heavysnow.

40. Birches especially grow in such areas because theycan stand the weight from an avalanche withoutbeing totally destroyed. Alders are also frequently

found in avalanche areas. Where avalanches arerelatively rare, the trees are taller, but when an oldtree is hit by an avalanche it breaks or its trunk isshattered. In old forest it may prove difficult todistinguish between damage caused by avalanches,by wind or by heavy snow. If, however, the treeslie pointing in the same direction like stripes orlanes down the mountain side, avalanches are themost likely cause.


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Loose masses

41. Large avalanches, and in particular those thatare set off in spring when the snow is wet, diginto the ground and carry stones and earth

along which are deposited in the lower parts ofthe track when the snow melts. In places wherethere are annual avalanches, the bottom of thevalley is strewn with suck material which iseasily spotted because of its fresh colour andbecause it is often found on top of new vegetat-ion. Sometimes it may be difficult to decide ifthe loose material has been deposited by small

streams or by an avalanche. Large avalanchesmay transport loose masses further away fromthe mountain side than small streams and alsofurther than a rock slide can reach. Anothercommon feature about material transported byan avalanche, is that gravel and stone are oftenfound on top of big blocks. The reason for thisis that this material was higher up in the snowwhen the avalanche stopped and remained on

the blocks when the snow melted. In placeswhere an avalanche comes down a steepmountain side and the transition to the bottomof the valley is abrupt, an avalanche will digholes in the ground because of its suddenchange of course. Thus a clearly visible hollowis made and the loose masses are depositedaround it like a wall. Often a small lake is

formed in these hollows. A similar thing can beobserved where large frequent avalanches endin rivers or lakes. Then lagoons are formedwith a reef of gravel, stones and sanddeposited by the avalanches.


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Figure 19Trees that have oftenbeen exposed toavalanches.

Figure 20Forest hit by anavalanche.

Figure 21Stone wall depositedby an avalancheending in a river.


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Preparations andtraining in terrainprone toavalanches

PreparationsMap

42. A map is one of the most important means of helpwe have in planning a route. The contour linesgive us a good picture of the terrain features andhow steep a mountain side is. These two factorsare decisive in identifying potentially dangerousareas of avalanches. Map series M 711 on a scaleof 1:50 000 and a contour interval of 20 m nowcovers almost all of Norway.

An avalanche may be sett off at an angle ofinclination down to 30. This corresponds to adistance between the 20 m contour lines of 0,7mm, and between the 100 m contour lines of 3,5mm. If the distance is shorter or similar to this, itis steep enough for an avalanche to be released. Inthis way possible release areas can be marked onthe map. It is important to realize that steep slopesless than 30 - 40 m high cannont normally be

identified by studying the contour lines. Thenthere is only the distance between the contour linesto work on. Maps on our scale are therefore notaccurate enough.

43. In appendix 4 a method of estimating the range ofan avalanche is described. This method puts alimit to possible avalanche cones. When the

release area and the avalanche cone have been


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marked on the map, the snow conditions haveto be considered with a view to possibleavalanches, if the area is to be used in militaryoperations. If the snow conditions are deemed

ustable and that an avalanche may be releasedthe area is to be considered dangerous and asafe outside or around this area has to bechosen.

44. When a potential hazard area is being considered,the first thing to do is to look for possible releaseareas. Start with maps and air photos, then make a

reconnaissance. All parts steeper than 30must be

looked upon as potential release areas and allleeward sides must be considered carefully.It is easy to underestimate potential release areas inthe upper parts of a mountain side when it isviewed from the bottom of the valley. The viewmay also be hampered by protruding rocks andridges so that the upper parts are not clearly visible.Therefore it is better to move from the mountain

side or, if possible, climb the opposite side to get abetter view. The most efficient method is using ahelicopter. Then it is possible to get close to therelease areas and also see them from differentangles so the best possible impression of theground can be obtained.

Avalanche map

45. The map shows areas prone to avalanches. It hasbeen made for the military for planning purposesand exercises and should not be used in othercontexts.Part of a snow avalanche map is shown in fig 22


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Snow Avalanche MapThis map indicates areas where snow avalanches may occur.The maps are produced for the Norwegian Military GeographicService and should not be used for other purposes withoutreservation. This map is divided into following zones:

Avalanche starting zonesTerrain steep enough for avalanche release.

Avalanche run-out zonesTerrain lying below starting zones, which may beexposed to avalanches.

Figure 22Avalanche mapwith suggestedprobability ofroute.


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The avalanche maps division intozones

46. The map is divided into the following zones:- Zone I : Avalanche starting zones

- Zone II : Avalanche run-out zones

Zone I

47. Zone I is identified by means of the maps contourlines and is to be marked where the distancebetween the 20m lines is 0,7mm or less and thereis no dense forest. The terrain is steep enough for

an avalanche to be released. Some steep areas areomitted since the forest is so dense that the risk ofan avalanche is considered to be small.

Zone II

48. Terrain below the avalanche starting zones that canbe reached by avalanches. Zone II is identified as aresult of an estimation built on experiences drawn

from many avalanche tracks (cp appendix 4). Insome places the line of zone II is drawn above thebuilt-up area even though it may be within the zoneII area.

Limitations of the avalanche map

49. The map shows the avalanche starting zones which

can be identified by means of the contour lines.Avalanches can therefore occur in slopes not steepenough to be included in the map. In creek bedsthe variation altitude is normally less than 40m andis therefore not indicated in the map. Snowconditions in creek beds often favour avalanches,thus being very dangerous.The map does not offer information indicating howfrequently an avalanche may be released. In certain


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areas there are yearly avalanches while in otherareas years may pass between avalanches.

How to use the avalanche map50. The avalanche map is well suited for planning

exercises and choice of routes. During planning,attention must be paid to the maps limitations andhow it is constructed. Because of the dominantwind direction some mountain side may appearwind-swept. For that reason it may be advisable tocross these mountain slopes if the choice of route

falls within zone I or II on the avalanche map.Even if the mountain slope appears wind-sweptthere may be snow in small river beds along themountain side. If there is any doubt chooseanother route.The prevailing wind direction must also be takeninto consideration in the planning. In Norwaymost precipitation is brougt by winds blowing froma north-westerly and a south-westerly direction.

This means that the mountain sides to the leewardaccumulate most snow and have the greatestfrequency of avalanches. In North Norway there isalso wind from a south-eastern direction blowingalong valleys and fjords. This wind often causesdrifting snow and a danger of avalanches also onwestern and nothern slopes.

51. Local people can offer valuable information on thelikelihood of avalanches in their areas. It is theref-ore advisable to mark the avalanche tracks basedon local knowledge. Mention of safe mountainsides should be taken with a pinch of salt if theshape and the angle of inclination indicate apotential danger of avalanches.The weather throughout the winter will indicate thecomposition of the snow layers. After long


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stable periods of cold weather with favourableconditions for growing metamorphism, it isimportant to realize that the snow may consistof loose layers and consequently be unstable.

Mild periods with temperatures above 0C will,however, cause stability in the snow. It is theweather over the last 3 days which is of thegreatest importance, and this period has to befocused on when considering the danger of anavalanche.

It is the weather

over the last 3days which is ofthe greatestimportance, and

this period has tobe focused onwhen consider-ing the danger of

an avalanche.


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How to operate inavalanche prone

terrainGeneral

52. The following factores influence exercises inavalanche prone terrain:

- weather, precipitation, wind and temperature- snow quality

- terrain and precipice.Figure 23Weather data in ameteogram


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Weather report

53. The latest weather reports and information fromweather stations are important. The meteogrammay also offer important information. The

meteogram is prepared by the NorwegianMeterological Institute and offers weather datagraphically at 0000hrs and 1800hrs daily. Theweather prognoses indicate what weather canbe expected in the nearest future.The prognoses are for:- 48 hours- 120 hours.

54. These may be updated daily or on demand.Meteograms can be ordered by fax or from themeterological stations in Bergen, Trondheim,Tromsoe or from the Norwegian MeterologicalInstitute in Oslo.

Precipitation

55. Data on how much snow has fallen over thepast 3-5 days have to be available. An amountof percipitation exeeding 30 mm over the past 3days is a sign that avalanches may be released.It is important to be aware of the fact that 1 mmprecipitation equals about 1 cm of newly fallensnow (fig 25). The snow depth should bemeasured in the actual site by using a ski stick

or by digging in the snow. This should be doneon a leeward slope.

Wind

56. Wind is also of great importance. How stronghas the wind been and from which direction hasit been blowing. If a fresh breeze or evenstronger winds have been blowing, there is


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reason to believe that snow has been drifting tothe leeward side. The wind is especially impor-tant if there has been a lot of loose snow in themountain up to the time the wind started.

Several incidents have proved that wind alonecan cause accumulation of snow on a slopewhere the avalanches were released.

Temperature

57. The temperature has great influence on thedanger of avalanches. A sudden rise to about 0

C normally increases the danger of anavalanche. If it has been warmer and then thetemperature falls, there is reason to assume thatthe danger of an avalanche will decrease.

Snow

58. Before there is any activity, the stability of thesnow must be checked - using the spade test

(see para 14). The test should be taken onslopes facing different directions because theconditions may vary from one mountain sideto the other, depending on which winddirections have been dominant. Also observenatural signs of warning:

- recent avalanches in the vicinity- skiing causes long rifts in the snow

- small flakes loosen if a ski is put down at anangle

- thundering sounds mean that a weak layer ofsnow has broken.

Ground

59. Choice of route must be decided by the stabilityof the snow. Stay away from the foot of


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mountain sides and avoid narrow brook beds ifthe snow appears to be unstable.If flake avalanches have been released in brookbeds the route must be along bare ridges and

hills. Utmost care must be exercised whenskiing down hill. It is difficult to judge the angleof inclination, and at great speeds it is easy toend up in steep areas where an avalanche maybe released.

Figure 24Flake avalanche innarrow valley.

Changes in weather

60. The danger of avalanches will all the time

change with the weather. It is imperative tounderstand that the risk can increase within afew hours, especially if the wind increasesmarkedly and there is much loose snow on theground, or if there is a sudden change ofweather after a long cold and stable period.In spring, be careful of steep mountain sidesexposed to sunshine. In addition there might beslush or brush avalanches. During periods of


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quick snow melting or heavy rain, avoidstaying in narrow valleys or where streams endat the bottom of valleys.

Figure 25Follow ridges be safe.

Choosing a safe route61. Be careful not to say that an area is safe if the

conditions indicate that a possible avalanchecan be released, even if avalanches have notbeen triggered for a long time.A booklet has been made, Army booklet 5-2,how to choose a safe route. It lists a number ofuseful points in choosing a safe route in winter.

The booklet is appendix 8 to this manual.

Crossing dangerous ground

62. Never enter an area if there is an avalanchehazard. Nevertheless, it is important to statewhat measures should be taken if a situationarises which makes it necessary to cross suchareas.


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A field training exercise is not reason goodenough to enter avalanche prone terrain.There are two emergency situations that need tobe covered under this heading because military

units may be involved:- a war time situation- inadvertently entering an avalanche prone area

In both cases the officer in charge has toevaluate the ground and choose a route whichin his opinion and from his experience offersthe least possible risk.

See UD 2-1 points 12450-12458 1996/97edition, appendix 9 to this manual. The latestissue of UD 2-1 covering these points shouldalways be used.

There are no

techniques ormeans whichcan guaranteea 100% safe

crossing ofavalancheprone terrain.


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The avalanche group

General63. Assessment of a possible avalanche hazard

starts when the planning of a field exercise hascome so far that the exercise area has beendesignated. The assessment is followed by areconnaissance before snowfall. The officer incharge of planning and running the exercisecarries the responsibility for the assessment.

The daily responsibility can be given to aspecially competent person. On staff level theresponsibility rests with S-2/G-2.Even if an avalanche group is established it isimportant to underline that personnel in thearea also carry responsibility for the currentassessment of the avalanche hazard and reportto the avalanche group.

Organization

64. A separate avalanche group is established inconnection with field exercises, brigadeexercises or exercises at higher levels. Mann-ing of the avalanche group is decided for eachexercise and depends on the geographicalextension of the exercise area and number of

participating units.


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65. The avalanche group is divided into:- staff which is part of the exercise directing

staff- 2 or more sections

The avalanche group is at the disposal of theexercise leader on the recommendation of thecommander of the group. The groups staffshould consist of 2 persons and be led by anofficer. Each section should consist of 2 - 3persons and be led by an officer.The avalanche group is administratively linkedto the exercise directing staff.

Figure 26The table oforganization forfield exercises of2 brigades orequivalent.


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Task and responsibility

66. The avalanche groups tasks andresponsibilities:

- gathering information on avalanche hazards

- processing of information- recommendation on use of exercise area

67. The sections tasks:- gathering information/assessment of avalanche

hazard in the area where units will operate- processing of information- advising tactical leader

- report to avalanche group staff- may also report directly to units involved or

the exercise directing staff.

68. Standing order for the avalanche group shouldinclude:

- Evaluation of the potential dangers ofavalanches in the exercise area

- Issuing an evaluation (0-4) 1-2 times a day

through the exercise planning staff. Theexercise planning staff notifies their units. Theevaluation should be issued for a 24-hour period. If required it should be issuedmore frequently. The first evaluation orwarning must be issued to the units beforeleaving for the exercise area.

- The warning is to have high priority

- One warning should cover the whole exercisearea

- Contact with meterological stations to gatherinformation on weather

- Contact with local police, highway authoritiesand local people for information onavalanches

- Offer assistance in case of avalanches, adviseon avalanche hazards in the accident area and


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along the route in and out of the area- Participation in the exercise directors planning

of the exercise when required- The leader of the avalanche group is to/should

participate in daily briefs for staff and umpires.

Equipment and materials

69. The avalanche group should have thefollowing:

- communications equipment- search poles

- spades- transponders- vehicle with trailer- 2 snowscooters- helicopter at disposal- thermometer- screen- snow profile forms- pc with modem and access to the meteogram

service at the Norwegian MeteorologicalInstitute

- tent/sheet- stove- sleeping bag- ground sheet- rations, SR 92 (meals ready to eat)

Communications equipment

70. The avalanche group must havecommunication with the directing staff andinternally within the group. Telephone is mostpractical to the directing staff and mobilephone internally. If a mobile phone is notavailable VHF stations like the AN/PRC - 77should be used.


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Spades

71. Used by the sections to check the snow.

Transponders72. Used by the members of the avalanche group

because they move in terrain which might beprone to avalanches.

Vehicle and trailer

73. Used for transport of snow scooters to diffe-rent places in the exercise area. The vehicle

should be a four wheel drive.

Helicopter

74. A helicopter should be available to theavalanche group (about 1 - 2 hours a day) toput patrols in critical places in order to coverthe exercise area as well as possible. Thepatrols can reach roads on their own and be

picked up by vehicles. A thorough recce willnormally take about 4 hours.

Thermometer, screen, snow profileforms

75. Used by the search sections to check the snowand then assess the stability of the snow.

Draw snow profiles.

PC with modem

76. Used to gather information from the Norwe-gian Meterological Institute on weatherpronoses for the exercise area.


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Bivouacking material and provisions

77. Used by the search sections to surviveoutdoors in case of bad weather.


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RescueGeneral

78. The possibility of survival in an avalanchedecreases rapidly and the rescue work must beaimed at finding possible casualties as quicklyas possible. Even with no apparent successduring the first hours, the effort should beeagerly maintained. There are examples ofpeople who have been alive after 24 hours andin some cases after several days. Rescue

work in an avalanche is a race against time!Those taking part in search and rescueoperations and particularly the officer incharge must consider the danger of potentialavalanches.

79. Rescue and search is divided into:- helping yourself- quick search

- organized search.

Helping yourself

80. If caught in an avalanche:- get rid of your back pack if possible- ski diagonally downwards toward a safe area- cover your face to prevent snow from getting

into your mouth and nose.If buried:

- cover and protect your face with your handsand arms to get breathing space

- do not struggle in order to avoid lack ofoxygen

- only shout when you hear someone on top ofyou. Do not expect to be heard even if youhear personnel moving in the snow above you.


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81. If you drive a bandwagon give full speed andtry to escape the avalanche by drivingdiagonally out of it. If you realise that youwill not succeed cut the engine immediatelybecause of the danger of carbon monoxidepoisoning. Remain in the vehicle as thisimproves your chances of being found.

Quick search

82. Quick search means that a unit or individualsafter an avalanche immediately start searchingwith whatever means available. The chances ofsurvival are reduced dramatically with the timeunderneath the snow. The quick search isimportant in order to save as many as possible.

Figure 27Deathrate inavalanches.


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Primary area of search

84. If possible the search should be limited to aprimary area, a small area with a good chanceof a find. Thus the possibility of finding

survivors will increase. The choise of a primaryarea of search is decided by:The sweeping-along-point and the furthercourse of the avalanche through the sweeping-along-point and the point where the snowaround the point of disappearance rested, givea good background to estimate the possibleplace where the person caught might beburied. It will not be possible to determine

83. How to carry out the quick search:- Decide on a primary search sector- Evaluate the hazard of avalanches- Start the surface search

- Carry out a tentative search together with asurface search

- Sound the alarm- First aid

Figure 28Choise of primaryarea of search.


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exactly where the person might be. Thereforean area called the primary area of search has tobe established.

b. The profile of the slope where the avalanche

has been started may give some clues. If thetransition is even, like a ski jumping hill, it isprobable that the person taken in theavalanche high up will lie somewhat behindthe front of the avalanche. If however, there isan abrupt transition, the snow from the upperparts of the slope will end on the top of thesnow at the foot of the slope. The person

caught by an avalanche at the foot of the slopewill therefore be carried a shorter way than aperson caught higher up.

c. Obstacles in the track of the avalanche causethe snow to be accumulated upstream orgathered downstream around the obstacle.

d. The speed of the snow is greatest on the sur-face and lowest along the edges of theavalanche. The person caught by the

avalanche may lie in eddies or in narrowpasses.

e. Traces like ski tracks running into theavalanche and items found must be consideredwhen deciding the primary area of search.

Avalanche guard

85. Avalanche guards are one or several personsposted in the avalanche area to warn personnelabout new avalanches. The avalanche guardwill be posted by the branch leader avalancheand equipped with means to warn, e.g. a verypistol or a weapon and ammunition. The guardshould be positioned in a safe place where hecan observe the area from which the branchleader thinks a new avalanche may start.


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86. Tasks:- Observe potential rupture zones- Sound the alarm immediately if an avalanche

is released.

It is decisive that that the warning procedure isrehearsed so that the alarm can be soundedalmost simultaneously with the release of theavalanche. The avalanche guard informsbranch leader avalanche in case weather ordarkness makes it impossible to observe thepotential rupture zone. The avalanche guard isto be changed at regular intervals.

Surface search

87. The whole avalanche is searched by personnelwalking through the avalanche looking foritems on the surface and listening for possiblecries for help from persons buried in theavalanche. Finds are controlled, for instance, bychecking what is at the end of a ski pole or a ski

etc.. Finds are marked.Figure 29Tentative search.


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Tentative search

88. Lack of time means that the search team mustwork as efficiently as possible. The pattern ofthe search must be carried through quickly but

cautiously. If search poles are not available,use ski poles. Remove the disk and push thestick down into the snow. A ski pole is tooshort but better than no stick or pole at all.Use the sharp end of the pole to get throughthe snow. There is certain danger of hurtingthe person buried in snow, but an injury of thiskind will be negligible compared to what can

be achieved if he is found as quickly aspossible. Personnel in the search line shouldnot carry avalanche ropes as this may make anevacuation difficult in case of a newavalanche.

89. The leader of the search section (should not bethe branch leader avalanche) is leader of thesearch line, the spade team and the markingteam. He organizes the search line so that the

pivot at the edge of the area acts as guide ofline and indicates with his search pole the firstpoint of search at the farthest corner of the area.The distance between the search pointssideway, should be 75 cm. This is achieved byputting each man with feet about 50 cm apartand about 25 cm to the next man in thedirection of the marker. A search line should

not consist of more than 10 men. If more menare available, several search lines should bearranged.Behind each search line there must be 4 mencarrying spades, marking equipment and sparesearch poles or sticks. The search area mustbe marked carefully.

90. The tentative search is carried out like this:


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- the search line leader controls the line and theintervals between the men and starts the workby ordering: Search!

- the searchers probe vertically down to 2

metres, not deeper. The search pole is movedcautiously but firmly. It is important to wearmittens to avoid icing along the pole

- if there is no find, the pole is withdrawnrapidly and the end of the pole is put on thenext point of search (about 75 cm ahead). Thesearch team need not keep their feet apart fromthe start of the search. In a real situation this

will prove impossible (big blocks etc)- the search line should keep quiet. The leader

of the line will constantly check the alignment.It is adjusted by ordering back those who areahead. The interval is maintained by checkingaganist the marker

- when all poles are at rest about 75 cm in frontof the holes already searched, the ordersearch is given, the line moves forward,

searches and marks once again- when a find is made, the message is sent down

the line to the search line leader and directly tothe personnel carrying spades. The searchpole remains standing. A new pole is handedover by one of the spade team. The searchcontinues

- when changing the personnel in the search line

those released leave their search poles down intheir last search holes. The crew walk insingle file along the poles the shortest way outof the area and downwards along the edges ofthe area.See also systematic search point 127.


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Warning

91. In case of an avalanche it is imperative to soundthe alarm - this may be a problem depending onthe distance to populated areas and the

possibilities for coming to assistance. Ifcommunications have been established animmediate warning is issued.The following are some guidelines for warningin case no means of communications areavailable:

a. Several people are presentOne person is dispatched in order to sound the

alarm, the others start a tentative search. Incase of bad or unpredictable weather conditions2 persons should be sent to fetch help.

b. Only two presentBoth carry out a tentative search for 45 minutes.Then one fetches help.

c. Only one presentHe/she conducts a tentative search for45 minutes and then fetches help.

92. These are guidelines for warning and should beused as such. A tentative search is carried outfor 45 minutes because the chances of findingpeople alive are greatest during this period oftime. Those who have survived for 45 minutesare often able to survive for another few hours.If there are few people present it is vital that

assistance is brought in to participate in therescue work.

93. First aid- locate the head of the casualty- make sure the respiratory passages are open- if necessary, start resuscitation and heart

compression


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- check injuries, careful with neck, back andchest

- if unconscious, put in stable position- compare moving a casualty with the danger of

further hypothermia. Cover thecasualty to keep him warm.

94. When digging out a casualty, priority should begiven to:Locating the casualty using search poles. It isnot clear how the casualty is positioned in theavalanche, therefore all digging should be

along the search pole. Release head first.First aiders and stretcher carriers are called.

Digging out and treatment ofcasualties

95. The most frequent causes of fatal accidents inavalanches are suffocation and hypothermia.Fractures of legs, back etc. can easily occur in

avalanches.While a first aider works withthe patient, personnel withspades make the hole largerand prepare access for thepulk out of theavalanche.

Figure 30Digging out casualty.


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Figure 31Table of organizationfor rescue leader.


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Planned search in an avalanche

Responsibility

96. The Royal Norwegian Ministry of Justice isresponsible for the execution of rescue andsearch operations. In case of an avalancheaccident the police will be assisted by civilianand military institutions and organizations.Because of the way a military unit is organizedit can be used effectively in such operations: insections, platoons and companies with trackedvehicles-, signals-, medical- and bivouacking

equipments and a staff.

97. Besides the military there are several institutionsand voluntary organizations educated andtrained for search in avalanches, among othersthe Red Cross.If the police have arrived and are running thesearch and rescue operation it is theirresponsibility to notify next of kin about injuredand dead. Normally a clergyman is used. Evenif the police have the responsibility it mayprove practical that the military help to notifynext of kin (if military personnel are involved inthe accident) and the police ask for this help.It is the responsibility of the hospital to reporton the condition of personnel admitted tohospital.

The Association of Norwegian Rescue Dogsand the Military Dog Training School have welltrained dogs. They are the quickest and mostreliable means of finding casualties in anavalanche. There is a strong need for closecooperation between the parties involved tooperate efficiently in search and rescueoperations. The aim is to save lives.

98. The responsibilities of the police in these


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operations include:- command and coordination of the operation- information to the media- identification of casualties

- notifying next of kin

Organization and tasks

The Main Rescue Coordination Centre (MRCC)99. Organized rescue operations in Norway are run

by one of the two Main Rescue CoordinationCentres (MRCC) in Bodoe and Stavanger. The

areas of responsibility comprise the watersnorth and south of the 65th parallel and the landareas north and south of the border betweenNamdal and Helgeland police districts. TheMRCC is run by the local chief constable withrepresentatives from the Military, NorwegianTelecommunications (Telenor), the PublicHealth Service and the Air Traffic Service. TheMRCC is responsible for running and

coordinating the rescue operation directly fromits centre, or the responsibility can be transfer-red to a police HQ, especially in case of minoraccidents. A police HQ given this task is calleda local rescue coordination centre (LRCC).

The Local Rescue Coordination Centre (LRCC)100.In principle the LRCC is organized in the same

way and has the same responsibilities as theMRCC. The chief constable who runs theLRCC organizes the centre according torequirements. The LRCC is normallyestablished on the premises of the police HQ.The LRCC informs the media. In case of arescue operation the LRCC appoints a rescueleader (RL) to organize and coordinate theefforts at the scene of the accident.


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101.The rescue leaders command post may beestablished in a building, a vehicle, a trackedvehicle or outdoors. It should be located asclose to the scene of the accident as possible

without causing problems for other activitiesgoing on. Communications must be establishedto the LRCC/MRCC from the CP.The rescue leaders CP will be manned by therescue leader and his staff.An evaluation of the extent of the accident, timeand means available decide the number ofpeople in the rescue leaders CP.

102.Responsibilities- command and coordination- communications/keeping a log- provide resources- intelligence- press and information

Personnel and tasks

103. The following categories of personnel can bepart of a rescue operation. One person maycover several tasks, e. g. keeping a log andintelligence. If there are personnel from severalorganizations and units participating in therescue operation one representative from eachof them will be part of the rescue leaders CP.

- rescue leader

- branch leader avalanche- operational medical leader- medical branch leader- branch leader order- keeper of log/intelligence- communications officer- logistics officer- press officer- intelligence officer


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104. Responsibilities of personnel in the rescueleaders command post (RLCP).

Figure 32Organization ofaccident area


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Rescue leader

105.The rescue leader is the local representative ofthe chief constable. All personnel in theaccident area are under his command. He

organizes the area, coordinates the efforts of hispersonnel and is responsible for providingnecessary resources through the LRCC. He is tocarry a green vest on which is printed rescueleader on the front and on the back. Therescue leader establishes a command post(RLCP) from where he directs the work.

Branch leader avalanche

106.He must be competent in areas of snow andavalanches and is resposible for evaluatingavalanche hazards and is in charge of thesearch in the avalanche.At the start of a rescue operation there may beno rescue leader present.Branch leader avalanche will then take over his

functions in the accident area.Branch leader avalanche has to carry an arm-band/vest to make him easily recognised by therescue personnel. He should havecommunications with the LRCC.

107.In the avalanche area the branch leaderavalanche directs:

- the search sections- the avalanche guard

108.The search section should consist of at least 15persons (cp. search line tentative search):

- leader - a search line of up to 10 persons- a spade team of up to 4 persons- a marking team (established when necessary;


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the number of persons will depend onthe situation).The number of search teams will depend onpersonnel and materials available and the size

of the avalanche. The tasks of a search teamwill be to carry out:

- surface search- tentative search- systematic search

109. Digging in case of a probable find and markingthe outer limits of the search area.

The search teams are made ready in the waitingarea. The search line is equipped with a searchpole for each man in addition to a couple ofsearch poles for the spade team. The spadeteam will be issued with spades and markingmaterials. The marking team is to mark theouter limits of the avalanche and other potentialareas pointed out by the branch leaderavalanche. In calm weather with no

precipitation marking may not be necessary.The marking team must be equipped withappropriate marking materials.

110.His tasks are to:- find a safe route to the site of the avalanche- estimate the avalanche hazard- post avalanche guard

- recommend how to organize the work at the sitetaking into consideration thehazard of new avalanches, wind direction androute into the area

- if necessary, mark the outer limits of theavalanche - decide escape route and routein and out of the avalanche

- lead the surface search and pick out the primaryarea of search


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- lead the search and the use of rescue dogs- cooperate with the logistics officer at the LRCC

about the need of resources

Operational medical leader

111.Operational medical

ud 6-81-9 (e) a guide to cold weather operations, booklet 9, snow, avalanches and rescue (1998)

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