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Home » Geological Disasters » Avalanche

Preventive and Mitigation Measures
All avalanche fatalities can be avoided. Two ways to accomplish that are to stop building communities in avalanche-prone mountain valleys and to prohibit recreation on mountain slopes. Both solutions, however, are impractical.
Rescue
Examples of various structures built to lessen the impact of
avalanches (Source: U.X.L Encyclopedia of Weather
and Natural Disasters)

  • In areas where avalanches frequently threaten communities, numerous steps can be taken to lessen their impact. On the slopes above roads or buildings, structures may be erected to either prevent avalanches from starting or to divert the path of an avalanche. Planting trees close together, for instance, can help prevent the formation of avalanches and stop the approach of ones that do develop. In starting zones, areas higher up on slopes where trees will usually not grow, large fences can be erected to keep the snow from sliding down. Large, slotted barriers called snow rakes can also be used to decrease the amount and speed of the falling snow mass.

Rescue
Avalanche barriers on Mannlichen Mountain,
Switzerland (Source: U.X.L Encyclopedia
of Weather and Natural Disasters)
  • Farther down the avalanche path, where roads or railroad tracks pass through, avalanche sheds can be built. A shed, constructed like an overpass with one end built into the slope, diverts the snow over the road or tracks to fall on the other side. Near buildings or other structures, heavy stone or concrete walls can be built to deflect the snow. In the lower reaches of an avalanche path, earth or rock mounds can also be constructed to break up the snow mass and slow its speed. An interesting design that provides direct protection to buildings is a wedge-shaped wall built in front of the structure with its point facing the slope.
  • In areas where roads and railroad tracks follow mountainous terrain for miles, the cost of these protective measures is prohibitive. In such situations, avalanche experts periodically use explosives-shot by cannon or gun, dropped from helicopters, or placed by hand-to dislodge the snow. This creates small avalanches and thus prevents the accumulation of heavier and possibly more destructive snowpacks.
Forecasting Avalanches
There are two basic methods of anticipating an avalanche hazard. One is the examination of snow cover structure for patterns of weakness, particularly those leading to slab avalanches. The second method is analysis of meteorological factors affecting snow depositions. In practice the two methods overlap and both are used. Emphasis on one or the other depends on local climate, pattern of snowfall, snow type, and avalanche characteristics. Both apply principally to winter avalanches in dry snow; forecasting wet spring avalanches depends on knowledge of heat input to the snow surface.

AVALANCHE DANGER SCALE
Degree of danger Avalanche release probability from different-types of slopes, consequences and suggested precautions.
Low Generally favourable condition. Triggering is generally possible only with high additional loads and on very few extreme slopes. Only sluffs possible and reach valley in small sizes. Valley movements are safe. Movement on slopes with care.
Medium Partly unfavourable condition. Triggering possible from the most avalanche prone slopes with low additional loads and may reach the valley in medium size. Avoid steep slopes. Routes should be selected with care. Valley movements with caution. Movement on slopes with extreme care.
High Unfavourable condition. Triggering possible from all avalanche prone slopes even with low additional loads and reach the valley in large size. Suspend all movements. Airborne avalanches likely.
All round Very unfavourable condition. Numerous large avalanches are likely from all possible avalanche slopes even on moderately steep terrain. Suspend all movements. Airborne avalanches likely.
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