researchers have developed a virtual reality simulation to “make things concrete” and alert coastal towns

At the end of the street, the sea crosses the perre, this concrete promenade that protects the city. The wave descends the steps, passes the casino and rushes into Etretat (Seine-Maritime). In a few seconds, black water envelops us. It would take us away if we were not in a simulation projected in virtual reality in the Cireve room of the University of Caen-Normandy. “With this speed of flow and this height of water, no one could stand”, explains geographer Stéphane Costa, one of the scientists behind the project.

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In the image, this violence is not simulated as it could be in the cinema: the restaurant chairs and the scaffolding are not projected in our direction by the wave. “What must be understood is that we are not making a disaster film. We are putting in images a scientific result”, explains Sophie Madeleine, deputy director of Cireve. Stéphane Costa’s team calculated what the February 1990 storm would give on the Normandy coast, with an additional meter of sea level. A rise in water levels under the effect of global warming towards which we are directing our greenhouse gas emissions by 2100.

Several cities, such as Etretat or Quiberville (Seine-Maritime), have the right to their minute thirty of simulation. Behind every video, “There is historical research, we worked with archives, testimonies. Then there are mathematical models to calculate the visualization”, explains Stéphane Costa. The project, funded by the Normandy region and the Fondation de France, requires significant resources: the room, which is also used by historians and doctors, cost 3 million euros. Producing a visualization takes about four months of calculations.

The objective is simple: to make coastal elected officials aware of the future of their cities. “The hazard cards that were presented to them did not work, a solution had to be found, traces the geographer, also chairman of the scientific council of the national coastline management strategy. There, they really feel these phenomena. “

It is not the elected officials of Etretat who will say the opposite. During a field trip on November 26, Stéphane Costa and Sophie Madeleine were able to bring this experience to life, thanks to a headset and a computer, to five elected officials of the municipality. “See this video, it makes things concrete”, testifies Clarisse Coufourier, municipal councilor. “It is to be disseminated to the general public and to our citizens”, estimates the first deputy, Bernard Le Damany. “It’s quite impressive, confirms the new mayor, André Baillard. As an elected official, you have to react, but in what direction? “

These visits are also an opportunity to discuss the solutions to be implemented. Stéphane Costa pleads, like the State, for flexible solutions, which can go as far as the relocation of activities. “Fighting against nature by putting in dikes, it is perhaps illusory and it is expensive. There are places where we can put defense works, but these works, we must put them with a clear logic, that to give yourself time to organize the coastline for 2100 “, he explains to elected officials.

Opposite, the latter cash in. “If I understand you correctly, enhancing part of the walk as we envisioned it would be just a bandage, analysis Joël Jacob, security assistant. There is a lot of work to be done with the population… Would that mean razing all the houses? ”. Stéphane Costa tries to reassure him. “Before saying to yourself: ‘We make everyone leave’, there are stages. It could be to say that the ground floor, we will no longer live there like today”, procrastinates the geographer, recognizing that“we are not going to switch from the situation of 2020 to that of 2100 suddenly”. At his side, Sophie Madeleine insists on the need to share information: “The ‘we didn’t know’ is the thing that hurts us the most. It’s to avoid that that we do all this work.”

During our visit to Etretat, we were able to show an extract of the simulation to Cédric, a resident of rue Prosper-Brindejont, the second artery of the city modeled by Cireve. “It’s impressive, especially the speed at which the water arrives”, reacts the metallurgist of 46 years, obviously struck by these images of the wave invading his street.

In the immediate future, this father feels protected by the three steps which raise the ground floor of the house. Ultimately, “this can be a problem”, he admits. Tenant, he is completely ready to evacuate the premises if necessary and says he is open to the creation of a buffer zone on the coast. “Either we protect or we evacuate. I’m more for evacuation, he explains. We are always trying to counter nature, but it is not sustainable. We want to concrete too much. At some point, we’re going to have to think about all of this. “