Submarine cables increasingly threatened by coastal erosion in France

2023-10-02 16:00:30
Orange Marine employees, in La-Seyne-sur-Mer (Var), March 1, 2016. BORIS HORVAT / AFP

On January 30, 2021, storm Justine hit the Breton coast. Waves, 7 to 8 meters, are common for this type of winter event, but the swell releases very strong energy. The next morning, the rare walkers on Pors-Carn beach in Penmarc’h (Finistère) discovered two large black plastic pipes coming out of the sand: these are the two transatlantic submarine telecom cables connected a few meters further into a landing chamber.

“There was no break in the cables, they are strong enough there, and therefore Internet traffic continued to function. But, this poses security problems, because these cables are supposed to be buried and invisible”explained Ludovic Carlier, submarine cable project manager at Orange, during a conference organized on June 2 by Finistère Mer Venta cooperative society of collective interest which supports entrepreneurs in the nautical sectors.

This also raises questions about the sustainability of these infrastructures, which are essential for global Internet traffic. “As much as they will withstand a first storm, if a second or third comes after it, it will be problematic”, recognized Mr. Carlier. Work to reconstruct the dune and stabilize it was undertaken after the passage of storm Justine.

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If the main dangers for submarine cables remain boat anchors, fishing nets, ground movements or violent currents, with the rise in water levels – 9.8 centimeters more since 1993, according to observations from the NASA –, coastal erosion will become an increasingly visible threat. Cables landing on beaches risk being damaged or even disconnected by coastal collapse or submersion. With its maritime facade and the numerous cables that connect to it (twenty-seven according to the Telegeography site), France is particularly sensitive to this phenomenon.

Forage horizontal

“We are not going to move the existing cable landing chambers, but for new sites we must take into account the retreat of the coastline”explains Michaël Trabbia, the general director of Orange Wholesale, the division of the telecoms operator in charge of the submarine cable activity, met on September 22, during the baptism at La Seyne-sur-Mer (Var ), of Sophie-Germainthe group’s new cable ship.

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So, to install its new Porge station (Gironde), which since this year has hosted the Amitié cable from Meta, Microsoft and Vodafone, linking Boston to Bordeaux and London, Orange has made its calculations. He chose the place on the Gironde coast where there was the least erosion and modeled the evolution of the coastline for the next fifty years. The cable was laid under the beach using horizontal drilling techniques, at a depth varying between 12 meters and 15 meters. The connection station, which can accommodate other cables in the future, was placed as a precaution 12 kilometers from the dune.