Survival

Shelter

Anyone who spends time in the wilderness should practice construction of emergency survival shelters. In a cold environment, a shelter becomes an extension of the microclimate of still, warm air created from body heat and trapped by insulated clothing. All shelters need adequate ventilation, which is especially important to consider when building a snow shelter.

Choosing the type of survival shelter to build depends on why the shelter is necessary and the availability of resources.

A properly designed shelter should permit easy and rapid construction with simple tools and give good protection from adverse elements. The type and size of shelter also depend on the presence or absence of snow and its depth, on natural features of the landscape, and on whether firewood or a stove and fuel are available. If external heat cannot be provided, a shelter must be small, waterproof, and windproof to preserve body heat.

General guidelines and considerations for choosing a location for a shelter include the following:

• Is the shelter needed solely for warmth or also for protection from wind and snow?

• Where should the shelter be built?

• What are the avalanche or rock-fall risks in the area?

• Avoid exposed windy ridges.

• Avoid any areas at risk for flooding (drainages, dry riverbeds).

• Avoid low-lying areas, such as basins that tend to collect the colder night air.

• A timbered area provides protection from foul weather, but can also block the sun.

• Select a shelter site where there is access to water.

• In windy conditions, a shelter should be built with the entrance at 90 degrees to the prevailing winds.

• Shelters can be built in small caves or indentations in a rock outcropping, in a “tree well,” or under downed trees.

• Environmental resources that can be used for building and insulating a shelter include small trees, branches, thick grass, or leaf piles.

• Snow is a good insulator because it traps the warmed air generated by body heat; however, direct contact with snow must be avoided.

• An insulation barrier between the snow and an individual can be created by using equipment, such as a closed cell foam pad or backpack, or it can be created by piling up small tree branches and boughs.

• The insulation layer, if using tree boughs, should be 25.4 to 30.5 cm (10 to 12 in) thick to allow for compression when sitting or lying on this layer.

Constructed Shelters

Plastic Bag Shelters ( Fig. 59.1 )

Large, heavy-grade (3 to 4 mil) orange plastic 208.2-L (55-gallon) drum liners make good short-term emergency shelters. Alternatively, heavy-duty trash bags can be used.

• 1.

  Cut an opening in the bottom end of the bag that is just large enough for your head, and then pass the bag over your head so that your face is at the opening.

• 2.

  When creating the hole, cut the plastic at 90 degrees to the fold to reduce the likelihood of the bag tearing along the seam.

• 3.

  A second bag, pulled over the legs, used in conjunction with the system described above, will form a one-person survival shelter.

Tube Tents ( Fig. 59.2 )

• Tube tents are inexpensive polypropylene sleeves that are 2.4 m (8 ft) long and provide a tubular shelter that is 0.9 to 1.5 m (3 to 5 ft) high, depending on the brand.

• A tube tent can be pulled over the body to provide a quick shelter or pitched as a “pup tent.” To do this, find two anchors (e.g., rocks, trees) that are the proper distance apart, tie a line to one of them, spread the tent out along the length of the line, run the line through it, and then tie off the other end of the line. The height of the line should be such that the tent can be spread out to accommodate the occupant.

• To avoid ripping, the tent plastic should be 3 to 4 mm thick.

• Tube tents can be improvised from two plastic 208.2-L (55-gallon) drum liners, which are 3 to 4 mm thick, or from large, heavy-grade household trash bags by opening the closed end of one bag, sliding it into the open end of the second bag, and then duct taping the bags together.

Tents and Bivouac Sacks

• Tents are generally comfortable and dry, but in very cold weather they are not as warm as snow shelters.

• Tents are preferable to snow shelters at mild temperatures, during damp snow conditions at temperatures above freezing, or when the snow cover is minimal.

• Bivouac sacks are carried by climbers on long alpine-style climbs or for emergencies. They are usually made of Gore-Tex or waterproof fabric and hold one or two persons. They pack small, are lightweight, and can easily be carried for an emergency shelter on any trip into the backcountry.

• Many modern packs have extensions, so when used with a cagoule or mountain parka, form acceptable bivouac sacs. The cagoule is donned, and the backpack is pulled on the feet and legs, extending the top of the pack as high up the body as it can be placed.

Natural Shelters

• Caves and alcoves under overhangs are good shelters and can be improved by building barrier walls with rocks, snow blocks, or brush to protect from wind.

• In deep snow, large fallen logs and bent-over evergreens frequently have hollows underneath them that can be used as small snow caves.

• Cone-shaped depressions around the trunks of evergreens (tree wells) can be improved by digging them out and roofing them over with evergreen branches or a tarp ( Fig. 59.3 ).

  

Snow Trenches ( Figs. 59.4 and 59.5 )

A snow trench is the easiest and quickest survival snow shelter and the one least likely to leave the diggers wet. If a shovel, large tarp, structural support items (skis, poles, trees), and a small fire, candle, or stove are available, a trench can be created that is as comfortable as a snow cave. It is easiest to dig a trench in a flat area. However, if the snow is deep enough, it can be dug out on an incline, keeping the trench itself level.

• 1.

  If possible, dig all the way to the ground. If the snow is too deep to dig to the ground, dig to a depth of 0.9 m (3 ft). If the snow is not deep enough, pile snow up around all four sides of the trench to make walls, until the total depth of the trench is 0.9 m (3 ft).

• 2.

  The trench width should be just slightly wider and 0.6 to 0.9 m (2 to 3 ft) longer than the person(s) that will be lying in the shelter. The additional length allows for a fire pit at one end of the shelter.

• 3.

  Ski poles, skis, or long tree branches are placed perpendicular to the length of the trench.

• 4.

  The trench is then covered with a tarp, leaving one end open for the entrance.

• 5.

  Secure the tarp on all sides by packing the edges into the snow.

• 6.

  Gently toss snow on top of the reinforced tarp to provide insulation to the shelter.

• 7.

  The snow pack on top should be 20.3 cm (8 in) or more.

• 8.

  The object is to keep the maximal amount of snow around and over the trench for optimal insulation.

• 9.

  If the trench is going to be wide enough to accommodate more than one person, the entrance should still be only wide enough for one person to pass through at a time. A narrow entrance is easier to close off and helps contain heat within the shelter.

• 10.

  A barrier can be created at the entrance by stacking backpacks or snow blocks, or hanging a tarp across the opening.

• 11.

  When the entrance is closed, a small votive-size candle or stove and the occupants’ body heat will raise the interior temperature to −4° to −1°C (24.8° to 30.2°F).

• 12.

  Higher temperatures should be avoided so that clothing and bedding will not become wet from melting snow.

• 13.

  Ventilation is necessary to prevent build-up of carbon monoxide within the shelter.

• 14.

  Anywhere that deep snow has been wind packed, as happens above timberline, the trench can be roofed with snow blocks.

• 15.

  The blocks are cut to a width of 45.2 to 50.8 cm (18 to 20 in), a depth of 10.2 cm (4 in), and a length equal to the length of the snow saw.

• 16.

  They are then laid horizontally for a narrow trench or vertically for a wider trench, set as an A-frame, or laid on skis (see Fig. 59.5 ).

• 17.

  Any spaces between the blocks are chinked with snow.