"Alpine Tsunami" - Galtür Avalanche

The Galtür Avalanche occurred on 23 February 1999 in the Alpine village of Galtür, Austria. It took less than 60 seconds to hit Galtür. At 50 metres (160 ft) high and traveling at 290 kilometres per hour (180 mph), this powder avalanche hit with great force, overturning cars, ruining buildings and burying 57 people. By the time rescue crews managed to arrive, 31 people – locals and tourists – had died. This avalanche was considered the worst Alpine avalanche in 40 years. Three major weather systems originating from the Atlantic accounted for large snowfalls totaling around four meters in the area. Freeze-thaw conditions created a weak layer on top of an existing snow pack; further snow was then deposited on top. This, coupled with hig.

Avalanche zones

Like most populated regions of the Alps, Galtür was hazard-zoned according to the perceived risk into red, yellow, and green areas. Red zones are considered highly vulnerable to avalanches; no development is permitted in these areas. Yellow zones pose a moderate risk to avalanches; development is allowed but structures must be reinforced to resist avalanches. Green zones are considered avalanche safe; development is permitted with no reinforcement required. Black zones present the highest risk; avalanches are almost a certainty.

The cause

In January 1999, a series of storms occurred bringing with them 4 metres (13 ft) of fine snow forming a huge snow pack on the mountains above Galtür. Later that month a melt-crust developed—the upper layers melting during the day and refreezing at night. The cause of the avalanches puzzled scientists for a long time. Although the area was prone to avalanches, never before had they occurred on such a scale as this, reaching the village. A complex sequence of events led to the event. On 20 January, an Atlantic storm was forming 4,000 kilometres (2,500 mi). Turbulent warm air from the tropics headed north, cooled, and swung back towards Europe. This initiated a series of storms. Combined with cold Arctic air coming from the north, there was a very dry, light snowfall exceeding 4 metres (13 ft). A massive snow pack formed on the mountains above Galtür. Northwest winds piled the snow to increasing depths. At Galtür, the snow bonded with ice and hence lasted longer than usual.

The resulting powder avalanche contained a central layer of which scientists were unaware. Known as the saltation layer, it was primarily responsible for the destruction of buildings. As new snow fell, the melt-crust became unstable until, on 23 February at 3:59 pm, it failed and caused an enormously powerful powder avalanche to crash down the mountainside, picking up more and more snow as it went. There was also 120km//hour winds which caused the saltation layer of snow to move causing this disaster.

Green Zone

As in the region, Galtür is risk-zoned for safety from avalanches; but it was the supposedly safe, green zone that was the worst hit. The Austrian government asked for assistance and thousands of people were airlifted out, using helicopters from both Europe and the USA. Galtür, however, lost much of its population and is no longer a major destination for tourists.[2]

Emergency response

United States Army UH-60 Blackhawk helicopter crew preparing to evacuate stranded tourists in Galtür, Austria, on 25 February 1999

Soon after the avalanche rescuers began to look for survivors; in 24 hours the rescuers saved 26 people. A rescue dog, Heiko, amply proved the value dogs have in avalanche rescue, saving many lives, as did a second dog, a Labrador-Alsatian cross named Jack, who was buried under snow for 24 hours. The day after the avalanche, 31 people were confirmed dead.

Aftermath

Outraged families demanded to know why the avalanche penetrated the supposedly safe zones and devastated Galtür. However, hazard zoning is based nearly entirely on the historical record, and there was no evidence of avalanches traveling so far on this track in the past. Since this disaster there have been renewed efforts to improve avalanche knowledge and forecasting so that hazard zones can be accurately predicted. This is particularly important if land use or climate changes render past information less useful. Response has included the extension of the hazard zones, with steel fences constructed on all mountainsides above the village to break up the areas where unstable snow packs can form, creating smaller shelves overall that reduce the size and scale of any future avalanches. A 300-metre (980 ft) avalanche dam directly protects the village. There has been rezoning, so the former Green zone is now of a higher risk zone.

In popular culture

The avalanche attracted media attention from all over the world, mostly for the magnitude of the rescue operation. It was also profiled on National Geographic's Seconds From Disaster in the episode "Alpine Tsunami".

h wind speeds created large snow drifts, caused roughly 170,000 tons of snow to be deposited.