With the flooding of the Loire, the flow at the Grangent dam, near Chavanay, was 100 times higher than normal.
Although the building held up, some bridges gave way under the force of the waters.
Faced with these phenomena, the intensity of which is amplified by climate change, it becomes necessary to adapt our infrastructures.
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Storms, thunderstorms, floods… the weather is getting carried away in France
In the Chavanay sector (Loire), where two bridges gave way under the power of the waters, the red flood alert was finally lifted this Saturday, October 19 in the morning. Much material damage was noted and the town was invaded by a torrent of mud. The Grangent hydroelectric dam has not failed, despite a flow rate 100 times higher than normal. The floodgates had to be opened to absorb the flow, giving the work a false appearance of Niagara Falls.
Which did not fail to attract a few curious people this Friday morning. “It’s scary!“, says a resident with a nervous laugh, in the TF1 news video at the top of this article. “It’s really impressive. You have to see it to believe it“, adds another.
Faced with such pressures, could dams like that of Chavanay, built in the 1960s, fail? “It’s impossibleassures Samuel Cremer, director of the sanitation and rainwater authorities at the Annonay Basin urban community (Ardèche). It is a dam which manages these floods, which makes it possible to check and manage the water height. Thanks to this, we can anticipate floods“, he explains.
The Grangent dam, which is subject to constant monitoring, made it possible to avoid the worst, estimates Antoinette Scherer, municipal councilor (SE) in Annonay (Ardèche). “We would probably have gone up to the first floors, which were not reached. Indeed, there would probably have been much greater destruction. We had no human losses, and that’s the most important thing“, underlines the elected official.
I was on the bridge and at that moment I started to feel vibrations under my feet
A resident of Chavanay.
Although the dams resist, two bridges have collapsed under the force of the waters. One near Pélussin, the other near Chavanay. A local resident filmed the scene. “I was on the bridge and at that moment I started to feel vibrations under my feet. I turned off my phone immediately. I didn’t ask myself any questions. I turned off the phone and ran“, he says, an excerpt of the video is broadcast in the report which accompanies this article.
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During bad weather, bridges can be weakened by the intensity of currents, but not only that, indicates Christelle Combescure, lecturer in civil engineering at the Saint-Cyr Military Academy. “All the elements which will be carried by the water following a flood, trees, cars, floating elements, which will hit the bridge and this will weaken it“, explains this specialist in the report. In the Chavanay sector, a third bridge, weakened by the torrent, must still be made safe.
