Sélune river revival after dam removal • Water News Europe

The removal of dams in the Sélune river in northern France is a success. Environmentalists recently found sea lampreys, eels and salmon.

The removal of dams in the Sélune river in northern France is a success. Environmentalists recently found sea lampreys, eels and salmon. After more than 90 years the river, which empties in the bay of Mont St Michel in Normandy, flowed freely again in late 2022. This was the result of the full removal of the Roche qui Boit dam and the removal of a bigger dam, at Vezins, in 2020.

Recently research director for the national research institute, Inrae, Jean-Marc Roussel described the first results of this ecological restoration operation as ‘spectacular’ in reference to the return of sea lampreys, European eels and Atlantic salmon. Scientists also found that the temperature of the opened river had decreased by 2C. Laura Soissons, an Inrae research engineer, who coordinated the monitoring, with colleague Jean-Marc Roussel, noted that vegetation had returned to the banks, despite the scale of the construction site in recent years. And the sediments, once trapped by the dams, have resumed their natural transit.

Resilient rivers

“We went from a fairly artificial ecosystem with unstable biodiversity, to something more stable and resilient,” Jean-Marc Roussel said. The Inrae scientist added this would be important to give the river ‘greater robustness in the face of the expected rise in temperatures’. Roberto Epple, Founder and President of the European Rivers Network (ERN) said:  “Dismantling this ancient hydropower dam and freeing up the Sélune is a landmark in Europe’s attitudes to its rivers.”

Biggest dam removal Europe

The removal of the 36-metre-high Vezins Dam was a historic moment as this was the biggest dam removal in Europe. Older dams are generally not designed for water discharge outside an accepted flow exchange. They are also likely to have reached high sedimentation rates which could threaten structural integrity. And as a result of ongoing and future climate change disturbances and predicted severe floods, serious threats to humans and infrastructures are now recognized, Dam Removal Europe says.

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Taxonomy

• River Engineering
• River Restoration
• Dams
• River Engineering