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Monday, 29 November, 1999, 12:56 GMT
Galtür: Anatomy of an avalanche
bunker Scientists had to dig their way out of the bunker

Scientists brought in to investigate February's catastrophic avalanche in Galtür, Austria, in which more than 30 people died, are about to publish their findings.

Their painstaking analysis of every detail of the event, from the complex dynamics of snow, to the study of wind and weather, has shown how an extraordinary chain of natural events led to a disaster in an area of the Alps thought to be relatively safe.

The BBC Science programme Horizon learned of the scientists' findings, having followed them for six months as they reviewed the evidence.

Independent inquiry

Dr Paul Föhn and Stefan Margreth, and colleagues, from the Swiss Federal Institute for Snow and Avalanche Research, were asked to lead an examination because of their expertise and because the Austrians wanted an independent inquiry.

The bunker contained radar equipment The bunker contained radar equipment
One key to understanding precisely what did occur on the afternoon of 23 February has come from a daring experiment in which scientists sat inside a concrete bunker as it was hit by a huge avalanche.

The bunker, which was filled with radar equipment, monitored the movement of the different snow layers inside the avalanche as the wall of powder went over the top and down the mountainside.

The data have allowed the researchers to build up a more realistic model of snow dynamics - one which explains how an avalanche can travel much further than previously thought possible and build in intensity as it goes.

This new thinking has been crucial to Föhn and Margreth's analysis of the Galtür event.

Strong winds

Meteorological records show that relatively warm weather in January was immediately followed by record snowfalls and strong winds in February. This led to the build up of an exceptionally large and unstable slab of snow on one of the slopes above Galtür.

When the slab eventually gave way, the avalanche came down on the village in a way only the latest computer models based on the bunker data could have forecast.

The scientists' calculations show that the block of snow that broke away on top of the mountain weighed some 170,000 tonnes. It moved at a speed of nearly 300 kph taking less than a minute to hit the valley floor. By this time, it had doubled in size. It was two minutes before the avalanche came to a stop. By then, the snow had covered what was thought to be some of the safest parts of the village.

The BBC's Horizon programme is broadcast on Thursdays on BBC Two at 2130 GMT

Galtür Galtür was victim of extreme events

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See also:
24 Feb 99 |  Europe
Avalanche buries Austrian town
24 Feb 99 |  Europe
Pictures from the disaster zone
25 Feb 99 |  World
Avalanches: A fatal attraction
25 Nov 99 |  Sci/Tech
High-tech clothing beats blizzards

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