Video Intro 2
There is a significant risk of avalanches occurring in glacial areas such as the Alps. They can cause widespread disruption, damage and sometimes loss of life.
Causes of avalanches
An avalanche is a sudden downhill movement of snow. It is a significant hazard to people living in, or visiting, glacial areas. A slab avalanche is the most dangerous form of movement. It can be caused by:
· heavy snowfall
· deforestation (for example because of new ski runs) making the slope less stable
· steep slopes, as this helps to increase the speed of movement
· vibrations (for example from an earthquake, noise or off-piste skiers)
· layering of snow - for instance where snow is already on the mountain and has turned into ice, and then fresh snow falls on top which can easily slide down
· the wind direction piling snow which can overhang a mountain
Effects of avalanches
An avalanche is able to obstruct anything in its path. Roads and railways can be blocked. Power supplies can be cut off.
A powerful avalanche can even destroy buildings.
People can also be killed.
90 per cent of people who die in avalanches trigger them themselves.
People usually die from a lack of oxygen when buried in snow, rather than from getting too cold
Case study: Galtür Austria
Galtür destruction
Galtür is a popular ski resort in Austria. Avalanches happen most years, but don’t usually reach the village of Galtür. On 23 February 1999 an avalanche raced down the mountain.
It travelled at 200 miles per hour, taking 50 seconds to reach the village. 31 people died, 26 were tourists and 5 were locals. Rescuers saved 26 people in the following 24 hours.
People in Galtür were stranded as roads were blocked. 16 buildings were destroyed or severely damaged.
Ski resorts were closed in the region, costing the industry £5 million for each day they were closed.
Management of avalanches
The areas in which avalanches occur may also be used for human activities, such as skiing. Villages and towns are also often located in the valleys. It is important for the people, economy, and the environment that avalanches are managed.
There are several ways in which avalanches can be managed:
Prediction
People try to predict when avalanches are going to occur. The Alps has an 'avalanche season' between January and March when most avalanches happen. Where avalanches are going to occur is hard to predict. Historical data, weather information and information about the actual snow on the mountainside is collected together to try and forecast the likelihood of an avalanche.
Explosions
Avalanches can be started deliberately in order to prevent the snow building up. This is one of the most important ways of preventing avalanches.
Communication
Signs of the risk of avalanches can be displayed in villages and also by the ski lifts. In the Alps the risk is assessed on a five-point scale. Areas can be sealed off which are considered too dangerous to ski on. Early warning systems are also used.
Land-use zoning
Land can be grouped into red, yellow and green areas. The red areas are considered too dangerous to be built on. The orange areas can be built on with restrictions, such as reinforcing buildings. Roads and railways can be protected by tunnels over them in the areas where an avalanche path is likely to travel.
Snow fences and barriers
These can be used to divert and break up the path of the avalanche.
Reforestation
Trees can be planted, increasing stability of the slope and helping to reduce the damage further down the valley.
