2024-03-01 22:11:24
After the exceptional floods in Geneva at the end of 2023, the effects of this bad weather are being felt in the depths of the Rhône. The gravel is piling up and dredging must take place earlier than planned.
An unusual boat is cleaning up at the start of the year in the Rhône. It is a barge that works like “a big vacuum cleaner” explains the pilot Michaël Capdeville in the 7:30 p.m. “We have a cutter in front which boils the materials and we suck them up. We spit them out further into the bed of the Rhône. Basically, we help the natural flow of sediments,” explains the employee of Geneva Industrial Services ( GIS).
This operation is necessary to allow the barge which transports Genevans’ waste to the incineration plant to circulate once more.
An exceptional situation
The consequences of last year’s historic floods are felt deep down. Never before seen for Cédric Bernard, head of river transport and special works at SIG. He particularly mentions the quantity of materials, which normally oscillates between 4000 and 5000 cubic meters for each cleaning operation. Currently “we are on 10,000 cubic meters”, specifies the specialist.
The calendar also had to be revised. Normally, this dredging is done once or twice a year, in summer or fall. But because of the floods, it was necessary to dredge in winter, which involves compromises for GIS.
Winter is indeed the reproduction period for salmonids. “This is not the best time to do it in terms of protecting biodiversity,” admits Gilles Garazi, energy transition director at SIG. “We were obliged to do it and therefore we obtained the necessary authorizations. But that is not what we want,” he explains.
Avoid possible future floods
The operation is not only useful for boats. It also makes it possible to better anticipate possible future floods. “In the middle of the city, where we don’t really want to see the level of the bed of the Arve rise by one or two meters, we would have a big security problem,” explains Etienne Monbaron-Jalade, head of the sector. hydrology and climatic extremes in the canton of Geneva.
“Reflections have been underway for several years to anticipate this arrival of gravel and to try to trap it somewhere and possibly extract it. But for the moment, the quantities involved are still under control and do not pose any real problems security”, analyzes Etienne Monbaron-Jalade.
The cantonal hydrologist estimates that floods like last year might be more frequent in the future. Dredging in winter might therefore become a recurrence.
Gianluca Agosta/lia
1709350773
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