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Repairing the scales for debris flows

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The Illgraben is unpredictable. In this mountain streambed above Leuk (Canton Valais), several debris flows, containing a destructive mixture of water, mud and rocks, thunder down into the valley each year. WSL has installed a series of measuring instruments here, including a set of scales, a so-called force plate, which was built into the streambed in 2003.  The aim is to use the collected data to understand the dynamics and flow behaviour of the debris flows better. By the time the scales were ripped out of their foundations and completely destroyed on 22 July 2016, they had weighed over fifty debris flows, each with an average weight of about 46 000 tons. On that day, the culprits, three enormous boulders weighing between twenty and thirty tons, were swept down into the valley in a debris flow. Thanks to a major investment of WSL, the scales can now be restored and optimized during the winter of 2018/19. At the same time, other measuring instruments will also be upgraded. (Lisa Bose, Diagonal 1/18)