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Avalanche sizes

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The European avalanche warning services divide avalanches into five size categories (based on the Canadian classification). The avalanche size is defined, among other things, by the potential damage caused.

Under this definition, fatal 'skier-triggered avalanches' are often classified as 'medium' or (barely) as 'large' avalanches and reaches considerable dimensions, being typically 150 m in length and having a slab size of some 50 m by 80 m and an average slab thickness of around 50 cm. This is equivalent to a slab volume of approximately 2000 m3 or around 400 tonnes.

 

Size 1: Small avalanche (sluff)

Potential damage:

Unlikely to bury a person, except in unfavourable runout zones

In extreme terrain there is a danger of falling.

Runout

Stops on a steep slope

Typical dimensions

Length:           10 – 30 m

Volume:               100 m3

 

Size 2: Medium avalanche

Potential damage:

Can bury, injure or kill people

Many avalanches that kill people are classified as 'medium'.

Runout

Can reach the end of the relevant slope

Typical dimensions

Length:           50 – 200 m

Volume:               1000 m3

 

Size 3: Large avalanche

Potential damage:

Can bury and destroy cars, damage trucks, destroy small buildings and break a few trees

Many avalanches that kill people are classified as 'large'.

Runout

Can cross flat terrain (well below 30°) over a distance of less than 50 m

Typical dimensions

Length:           Several hundred metres

Volume:               10,000 m3

 

Size 4:Very large avalanche

Potential damage:

Can bury and destroy trucks and trains Can destroy fairly large buildings and small areas of forest. Very large avalanches can occur at danger level 3 and are typical of danger levels 4 and 5.

Runout

Traverses flat terrain (well below 30°) over a distance of more than 50 m

Can reach the valley floor

Typical dimensions

Length:           1 – 2 km

Volume:               100,000 m3

 

Size 5: Extremely large avalanche

Potential damage:

Can devastate the landscape and has catastrophic destructive potential

Typical for danger level 5

Runout

Reaches the valley floor

Largest known avalanche

Typical dimensions

Length:           Approx. 3 km

Volume:               > 100,000 m3