Laurent Quartier remembers well February 27, 2010, the day of storm Xynthia. “It happened unexpectedly. We didn't expect it at all.» Now retired, this resident of Saint-Nazaire (Loire-Atlantique) then worked at the Departmental Directorate of Territories and the Sea (DDTM). The following days, he went to take water readings in Méan-Penhoët, a district of the city at risk of submersion. In the small port of Brivet, named after the last tributary of the Loire which flows into the river, small brass markers keep the memory of this tragic event. They indicate the height of the water reached, around thirty centimeters for the most exposed houses. Certainly, we were far from the two meters recorded in neighboring Vendée, where 47 people had died. Laurent has not experienced any flooding at his home, but he has since made some adjustments, notably valves, in order to avoid rising water. Smiling, he sighs fatalistically: “For me, it’s not something abstract, storms.”
Whether along its coastline or in the Loire estuary, in Pornic, Pouliguen or Pellerin, the Loire-Atlantique includes several sectors at risk of submersion or erosion. And even if, according to the projection maps, the department seems less exposed than others in the immediate future – we are thinking of Seine-Maritime or Haute-Corse – its low relief weakens it in the longer term, with numerous low areas, behind the coast, separated from the ocean by simple dune cords. The area is also highly urbanized: “A territory where land artificialization is high, with few natural buffer spaces”notes Marc Robin, of the Regional Observatory of Coastal Risks, an organization attached to the University of Nantes, who works with his team to inform communities and state services about the risks involved.
In Saint-Nazaire, after the publication of the 2016 coastal risk prevention plan (PPRL) which demarcated areas at risk of submersion, the municipality adapted its town planning plan. In the Méan-Penhoët district, a dike was built in 2017, a stone wall leaning against a mound and pierced with openings towards the small marina. An alert system has also been set up with Météo France. In the event of an emergency, he plans to close the passages using cofferdams, removable barriers. In terms of town planning, “There are areas where we can no longer build, or in a regulated manner. The houses are supposed to be equipped with a refuge floor or roof access for emergency services. The electric meters had to be sheltered”explains Guillaume Hainigue, natural risks and adaptations manager for the urban area.
It is difficult to know, however, if the residents really carried out the obligatory work. “Housing vulnerability diagnoses are covered by the Barnier fund, as well as the recommended work up to 80%, but we do not have exhaustive figures listing who carried them out,” explains the expert. Laurent Quartier, who has lived for thirty-seven years in this working-class sector a stone's throw from the Chantiers de l'Atlantique, an area of modest and often single-storey houses, confirms: “People sometimes have difficulty understanding why they are in red on the map and their neighbor is in blue. And it is true that there were few of us at the public information meeting, and even fewer carrying out the diagnostics and then the work.”
“One day we will have to move”
This is the problem for public authorities: we must anticipate a change which will undoubtedly spread over several decades. “For the moment, the impact of rising sea levels is not visible on a daily basisconstate Guillaume Hainigue. These are rather possible submergence phenomena during big storms. but which come to shock public opinion. “The difficulty is to put temporality into all of thiscontinues Eric Provost, elected in charge of environmental issues in Saint-Nazaire. We are in the long term and that makes it difficult to take into account.” Especially since the projections remain vague. “If we look into the future, the sea level is rising, its temperature is increasing. Storms expected to be stronger, rainierunderlines academic Marc Robin. However, we cannot position the coastline precisely.”
Although it seems difficult to predict the future of the Méan-Penhoët district in fifty years, predictions are nevertheless possible. In Saint-Nazaire, the tide gauge installed in the port notes a rise in the water level of 20 centimeters since 1860. IPCC scientists predict the same thing for the next twenty-five years, i.e. 20 cm by 2050. The along the Brivet dyke, on this foggy morning, Guillaume Hainigue knows it well. “It is certain that in the long term, the houses of Méan will have to be redesigned”he explains modestly. Before summarizing: “Protecting yourself is not a solution for the future. One day it will have to be moved. Not burying your head in the sand means reviewing planning priorities.”
We also need to think about the waterfront differently. “Today, it costs less to strengthen coastal defenses, to dam, to replenish beachesanalyse Marc Robin. The day this cost exceeds that of relocation, which will not take long to happen, the trend will be reversed. If the first climate refugees on the coast made the headlines – like those from the Signal building, in Gironde, evacuated in 2014 and finally compensated in 2021 after seven years of procedure, or even the upcoming move of four medical establishments social located in Saint-Brévin-les-Pins decided by the Loire-Atlantique department – these situations remain exceptions. Financial and legal tools need to be found. With a central question: who will cover the development costs, then those of travel? “We can see it clearly, the State is withdrawing, local authorities are called upon to organize themselves”denounces Guillaume Hainigue, project manager for the urban area.
And the bill promises to be heavy. “Communities will already have to secure roads, public facilities, and this will be the priority”defends the elected representative of Saint-Nazaire Eric Provost. How will private homes be treated? “We will have to find adequate solidarity mechanisms, create a fund”advances Marc Robin, who goes further: “Devalue properties to dissuade residents? But who will buy them back? For Eric Provost, the answer is clear: “The public is not there to compensate the private sector. Especially since insurance prices have already started to increase for communities.” The latter may even explode in the coming years and exclude certain phenomena, such as submersion. “Our role is to inform the population as much as possible in advance,” he continues. However, awareness does not follow. You only need to look at property prices, still at their highest on the coast, to realize how far there is still to go.
“The risk is to give rural people the impression of being sacrificed”
Going back into the estuary, the Adapto project of the Conservatoire du Littoral is working precisely on this awareness, but in unbuilt areas. Land owner, this public establishment questions the rise of water on some of its plots. In Frossay, the banks of the Loire have always been included in the maritime domain: the water of the river is salty and its levels fluctuate with the tides. Here, in an estuary subject to rising seawater downstream and the drying of the river upstream, no risk prevention plan has yet been published, despite the presence of numerous industries and different Seveso sites. Juliette Thibier, responsible for the Adapto project in question, explains: “It’s quite subtle, but we can already see the change. There are threshold effects, greater silt deposits in the meadows. New watercourses are formed, reed beds develop. For the moment, we continue to cure, but the idea is to see how we welcome the water in the long term…”
Opposite it, on the other side of the Loire, the coal factory of Cordemais and its red and white chimneys drown in the gray sky. On the river, two fishing boats are stationary, their nets raised above the brown waters, while a herd of cows graze on dry land, lush and damp meadows punctuated by clumps of reed beds. In a highly artificialized area, “a vegetated sector necessarily slows down the waves during potential submergence, believes Juliette Thibier, and offers greater resilience to climate change. While the academic Marc Robin proposes the creation of “buffer zones” which could absorb water and “preserve more urbanized sectors”, the project manager thinks that the equation will prove more complicated on the ground: “It’s tricky to explain to people. The risk is to give rural people the impression of being sacrificed.” To carry out the project successfully, we must bring everyone concerned around the table: farmers, naturalist associations, municipalities, hunters, citizens… If, in Frossay, no house is directly affected, this is not the case in Corsept, a few kilometers away. Juliette Thibier details: “The idea is to give time for adaptation by asking the right questions together: until when will we maintain the current dike and repair it? When do consequences no longer become acceptable? When is the relocation planned? Even if, once again, we don’t have a crystal ball.”
