Classified as a Natura 2000 area, the Breton bay is the scene of a century-old struggle between man and the sea. Since the construction of a dyke in the 13th century by monks, several hundred hectares of agricultural land have been reclaimed from the sea. Over the centuries, four dykes have been erected, pushing back the coastline accordingly.
However, the planetary prospects of sea level rise and submersion already seem a reality to Lancieux.
“Even if the sea only rises 60 cm by 2100, we know that our dikes are neither high enough nor strong enough. Today during high tide, the sea already licks the top of the dikes”, recognizes Michel Aussant, municipal councilor in Lancieux.
Faced with the challenges of tomorrow, the Conservatoire du littoral (CdL), owner of part of the land, has integrated the bay into the “Adapto” experiment, carried out since 2018 on ten sites in France, in order to imagine local solutions. “based on nature”.
This includes supporting communities, which have had flood prevention skills for four years.
The subject is all the more significant as one of the dikes opened at the beginning of 2020 under the combined effect of weather and swell, allowing the water to regain its place and the pastures to disappear in front of the obione and glasswort, characteristic of salt marshes.
“We had already repaired it several times but the emptiness of this fight is no longer to be demonstrated. We were building with public money what the sea had fun demolishing. We had to change the paradigm”, summarizes Gwenal Hervouët, deputy regional delegate of the CdL. The decision was therefore made not to close the breach and to make it “an opportunity”.
– “S’adapter” –
“Today this landscape shaped by man is no longer adapted to climate change. Between the strategy of resisting or adapting, the Conservatory and the communities have chosen to adapt, especially as rebuilding the current dike would cost several million euros”, assures Gaëtan Doineau, coastal guard at the community of communes Côte d’Emeraude.
One of the solutions consists of supporting the return of the sea to formerly poldered areas and recreating a wetland which would act as a buffer between sea and land by absorbing part of the energy of the waves during storms.
“It is not a question of waiting, arms crossed, for the sea to rise”, underlines Mr. Doineau.
Several measures have thus been taken to prevent the risk of flooding in Beaussais-sur-Mer, neighboring Lancieux: relocation of a path and a sewage lifting station, closure of a road.
A house built after the dike, which found its feet in the water in May 2021, had to be evacuated before being bought by the Conservatoire du littoral.
But accompanying the retreat of the coastline is not possible everywhere in the bay. “We can step back and then at some point, we also have to defend ourselves,” warns Michel Penhouët, in charge of the environment at the community of municipalities.
The law obliges the local authorities to maintain the embankment on the Lancieux side, insofar as the latter protects around thirty dwellings, a campsite and a golf course. “We have blocked an extension of the campsite towards the sea but in the long term, a new dike is envisaged further upstream”, indicates Michel Aussant.
Displacement, redemption, protection, “to communities to make their choice”, specifies Gwenal Hervouët. Because should we build a dyke in 2050 that will have to be raised in 2100? “The problem is that we don’t know how much or how fast the sea will rise,” observes Mr. Penhouët.
Some residents, however, have the impression of having been “forgotten”, like Mr. Noël, who, without being opposed to the project, would like to have the guarantee that his house, built in the 18th century, will not end up under water.