1999 Galtür avalanche
The Galtür Avalanche was an avalanche that occurred on February 23, 1999 in the Alpine village of Galtür, Austria. The avalanche killed 31 people and is considered the worst Alpine avalanche in 40 years.[1] Three major weather systems originating from the Atlantic accounted for large snow falls 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 high wind speeds creating large snow drifts, caused roughly 170,000 tons of snow to be deposited.[2]
The zones
Like most populated regions of the alps, Galtür was hazard zoned according to the perceived risk into red, yellow and green areas.
- Red Zone- Highly vulnerable to avalanches; no development permitted
- Yellow Zone- Moderate risk; development is allowed but must be reinforced to resist an avalanche.
- Green Zone- Avalanche safe; development is permitted with no reinforcement required.
The cause of the avalanches puzzled scientists for a long period of 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: 4000km away, on January 20, an Atlantic storm was forming. Turbulent warm air from the tropics headed north, and, cooling, it swung back towards Europe. This started a series of storms. Combined with cold arctic air coming from the north, there was a very dry, light snowfall exceeding 4 meters. A massive snowpack formed on the mountains above Galtür. Northwest winds piled the snow to increasing depths. A melt-crust developed in late January, formed when solar energy thaws the upper snow layers in the day, but it then refreezes at night. At Galtür, it bonded with ice and hence lasted longer than they were generally known to. The resulting powder avalanche contained a central layer scientists were not previously aware existed. Known as the saltation layer, it was primarily responsible for the destruction of buildings.[3]
The avalanche
The avalanche occurred on February 23, 1999 at 3:59PM in Austria, when the frozen layer of snow (melt-freeze-crust) failed.[4] Due to the cold conditions, snow with a very low density (between 50 and 70 kg/m³) was formed. This caused a massive powder avalanche traveling at around 186mph (290km/h) down the mountainside. As it travelled down the mountain, the avalanche picked up twice the amount of the initial snow volume of around 170,000 tonnes.[5] The avalanche was estimated to contain around 300,000 metric tonnes of snow; it had a height of around 100m (300 ft.) at its leading edge and took only 50 seconds to reach the village. The avalanche went into the village's Green Zone, destroying seven modern buildings and causing extensive primary and secondary damage as well as burying 57 people. Many people died of asphyxiation from inhaling and suffocating on the aerosol-type snow due to its low density.[3]
Aftermath
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. The day after the avalanche, 31 people were all confirmed dead.[6] 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 shelves can form, creating smaller shelves overall that reduce the size and scale of any future avalanches. A 300m avalanche dam directly protects the village.
In Popular Culture
The avalanche attracted media attention from all over the world, mostly due to the magnitude of the rescue operation. It was also profiled on National Geographic's Seconds From Disaster in the episode "Alpine Tsunami".[6]
References
- ^ British Broadcasting Corporation (1999-11-25). "Science & Nature - Horizon - Anatomy of an Avalanche". BBC. Retrieved 2011-01-12.
- ^ (PAUL FOEHN)
- ^ a b "Revision:Galtur Avalanche". The Student Room. Retrieved 2011-01-12.
- ^ "Mission report of the Tyrolean emergency management organisation". Retrieved 2011-08-03.
- ^ "SCI/TECH | Galtür: Anatomy of an avalanche". BBC News. 1999-11-29. Retrieved 2011-01-12.
- ^ a b "Seconds From Disaster | Alpine Tsunami | National Geographic Channel". Channel.nationalgeographic.com. Retrieved 2011-01-12.