the Winter Hazard in the Mountains
Avalanches present a considerable safety risk in the mountains – both inside and outside areas of permanent settlement. Following a severe snowfall or through the warming up (moisture permeation) of the blanket of snow, snow masses become detached on steep slopes and hurtle downhill at high speed.
The avalanche breaks loose either as one large sheet mass (snow slab) or through snow loosening here and there (loose snow). According to the composition of the snow, a distinction is made between dry and wet snow avalanches, and according to their movement, between flow and powder snow avalanches.
Powder avalanches can reach speeds of up to 250 km/h and extremely high pressure forces. Often, one can observe mixed, part flow and part powder snow, avalanches. The speed and extent of wet snow avalanches is less as a rule, although the amount of destruction can be very great due to their high snow density.
In the Alps, extreme avalanche winters, which claimed many lives, have repeatedly occurred: e.g. 1689 (256 deaths in Tyrol, Vorarlberg), 1951 (135 deaths in Carinthia, Salzburg, Tyrol, Vorarlberg), 1954 (143 deaths) and the 1999 avalanche disaster, which claimed 38 lives in the Paznauntal.
Avalanches are therefore widely known as the “White Death“. Thanks to extensive safety measures, avalanches resulting in deaths only seldom occur in areas of permanent settlement nowadays - by contrast, the number of victims on unsecured terrain is constantly growing.
The opening up of the Alps to tourism in the 20th century has made protection against avalanches into a task of central importance. Steel snow bridges and nets are being installed in areas prone to avalanches, while the diversion and slowing of avalanches is accomplished through earth dams and avalanche breakers.
For a long time, individual residential buildings have also been protected by setting up earth wedges (built up to the same height) in front of them. Avalanche-proof building in accordance with the latest technology includes reinforced outer walls, a stable roof and building construction and pressure-proof “avalanche windows”. In order to secure traffic networks, warning systems have been installed in some places, although affected routes are usually closed or highly threatening avalanches preventively blown up.
Avalanche warning commissions assess serious avalanche threats at the local level. In addition, avalanche warning services that classify the avalanche threat according to a 5-point danger scale. The weather, snow and avalanche conditions are kept under a continuous watch and preventive measures are recommended.
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