Sunday, July 1, 2012

Melting permafrost threatens Swiss villages

Ray Smith in IPS: Melting glaciers are the most visible effect of global warming in the Swiss Alps. Meanwhile, permafrost is invisible and melting too, often causing rockfall and massive debris flows, ultimately threatening mountain villages.

Guttannen, home to 310 residents, is a tiny village in the Bernese Alps, the last one that travellers drive through on the way up to Grimsel Pass. It’s spring and the snow is retreating from the steep slopes of the valley. As the pass is still closed, calm reigns in the picturesque village centre. Only cowbells and the rushing of the nearby Aar river break the silence.

For some residents though, living in Guttannen has become rather uneasy and, on the long term, even dangerous. The root cause of the peril lies further uphill, in the northeastern flank of the 3,282 metres high Ritzlihorn. In July 2009, a huge rockfall had occurred and since then, massive debris flows have roared downhill each summer.

“These mudslides as well as the volume of transported rubble have grown from year to year,” says Nils Hählen, hydraulic engineer at the cantonal public works service. “The debris partly ends up in the Aar, lifting and widening its channel.” Within three years, 630,000 cubic metres were transported into the river, increasingly endangering civil infrastructure.

In summer, after heavy rainfall, the only road leading through the narrow valley often has to be temporarily closed. A house near the river already had to be taken down, the local sewage treatment plant may be next. Since 2010, the debris flows reach as far as the hamlet Boden, threatening ten houses and 30 inhabitants....

The Oberarsee in Guttanen, Switzerland, shot by V. Raz, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

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