The Eiffel Tower with its feet in the water, the Louvre transformed into a swimming pool or even the out-of-service Gare de Lyon: this is the disaster scenario of a major flood in the Paris region that the authorities want to avoid at all costs by implementing place anti-flood devices on the banks of the Seine. One of them, brand new and unique of its kind, has been tested since January 13 on the border of the departments of Yonne and Seine-et-Marne.
The principle is simple, it involves pumping water from the river to lower its level. The eight pumps installed on the banks of the Seine were therefore activated for the first time to a deafening noise. “This water goes inside the pilot box, which is in fact a belt of dikes, a square of 2 km on each side and 2.50 m high and this will make it possible to retain this volume of water”, explain Baptiste Blanchard, the general director of Seine Grands Lacs, the operator of this device called “pilot locker”.
This work could make it possible to lower the level of the Seine by around 15 centimeters, but it will only be put into service in the event of a major risk. “We do it when the flow of the Yonne and either the Seine or the Loing is sufficiently high and there is a risk of major flooding for the Paris region.
“In 2016 or 2018, we had significant floods which would have led to triggering this pilot trap.”
Baptiste Blanchardat franceinfo
According to their calculations, 15 million euros of damage could thus be avoided on average each year. An anti-flood system in addition to the four large reservoir lakes of Champagne and Morvan, responsible for regulating the Seine.
But for local residents, this system represents a certain constraint. This water is in fact not stored in an artificial basin. It is discharged into a vast wetland made up of ponds, vegetation and paths, a place popular with residents who come to walk, fish or hunt. For them, there is no question of entering it when it is in the filling phase. Moreover, when we approach it, the phones start to vibrate with a sound signal and a message asking to immediately evacuate the interior of this area.
The mayor of the town Stéphanie Banos concedes that it is a project which raises some concern, particularly for the owners of plots which will be flooded. Compensation and restoration of their land are planned once the area is emptied. As for wild boars, deer or hedgehogs that roam these areas, they too must evacuate. “There was a scare to evacuate all the larger specimens and nature will mean that, normally, all the small ones will leave when they see the water coming, it’s true that this is one of the concerns, we is due to our nature and its diversity. For its part, the France Nature Environnement association evokes a disproportionate upheaval for biodiversity.
However, this work would not be enough to prevent the capital from being flooded. It will not be able, on its own, to completely protect Paris and Ile-de-France from a 100-year flood, that is to say a flood which has a one in 100 chance of occurring every year. The last one dates back to 1910. “If the St Lazare station was bathed in water, it was much worse on the Invalides station side. The Paris of 1910 was a kind of improvised Venice, without a gondola or romance”can we hear in sound archives.
Ludovic Faytre, head of Major Risk Studies at the Paris Region institute, confirms this: “We will not prevent the flood. We know it will happen, but we cannot predict exactly when, give or take a few weeks. It will not be at all the same as it was at the time, we know that there will be no metro, no RER, that we will have difficulties supplying drinking water. We have many things that can malfunction and which contribute to the vulnerability of our territory.
According to a survey carried out by these specialists, awareness of the risk remains low among the population, despite the last two major floods of 2016 and 2018.
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