Ten years of reflection and thirty months of work were necessary to begin filling the first in a series of nine structures to protect Paris from a major flood. Supported by the Métropole du Grand Paris and Seine Grands Lacs, the manager which manages the flow of the river and its tributaries (Aube, Marne and Yonne), this hydraulic structure should help protect the capital and the towns located on the banks of the Seine. floods. Called Seine Bassée Pilot Locker, the first in the series covers 360 hectares and is located in the south of Seine-et-Marne. The investment of 114 million euros should make it possible to lower the level of the Seine by a maximum of 15 centimeters. Very insufficient in the event of heavy flooding which could increase with climate change.
The alert from the Court of Auditors
But this project is in line with the report of the Court of Auditors, which in 2022 published a report entitled “Insufficient prevention of the risk of flooding in Île-de-France”. She recalled that according to “comparisons made by the OECD, the level of protection of large metropolises is much higher than Paris”. Citing Frankfurt or London, the report defended the La Bassée temporary storage project planned in the 2007-2013 Seine plan. “It consists of arranging ten [neuf en réalité, Ndlr] dammed areas in the major river bed between the downstream of Bray-sur-Seine and the commune of Marolles-sur-Seine as well as to operate storage by pumping the waters of the Seine. Unlike the four reservoir lakes, the Bassée storage project will have the sole purpose of defense against floods.
“Coupled with the action of the four reservoir lakes (- 70 cm), this complete system of ten traps (- 40 to 60 cm) would make it possible to maintain the Seine below the level at which the main damage appears (maintaining the water line water below 7.30 m in Paris Austerlitz)according to the Seine Grands Lacs establishment, indicate the Sages of rue Cambon. Thanks to the storage of 55 million cubic meters, it would save 1.6 billion euros for a 1910 type flood and 500 million euros for a 1955 type flood.
Lack of efficiency and ecological damage
This project was contested in court by local residents’ associations and the Nature Environment Federation (FNE) of Seine-et-Marne and Île-de-France. The first appeal filed in 2020 was dismissed in 2023. The FNE appealed in July 2023 and is still awaiting the verdict. “There are legal remarks, denounces Jean-François Dupont, co-president of the FNE Seine-et-Marne to L’Usine Nouvelle. The public inquiry was botched during Covid-19. And this overall project – if all the lockers are completed – was initially budgeted for an amount of 660 million euros. Today, it is approaching a billion. »
-The first compartment is surrounded by a 7.8 kilometer dike allowing 10 million cubic meters of water to be injected with pumps. “Basically, the trap is located in the Bassée wetland, the largest in Île-de-France.continues Jean-François Dupont. The first trap has already disrupted a good part of this wetland. Animal species were hunted.” Seine Grands Lacs ensures “renaturing” the area with a reconquest of biodiversity. But at the FNE, we consider that these are not the same plant and animal species. The environmental association also denounces “the fairly reduced efficiency of this project, the estimates of which have varied over the months” and fears that all its effects will be wiped out by another project, that of the large-scale canal supported by Voies navigables de France between Bray-sur-Seine and Nogent-sur-Seine.
The FNE is proposing an alternative project to these lockers based on nature. She recommends avoiding intensive crops which strip the soil. At the same time, it proposes favoring the flooding of fields and meadows if necessary in exchange for financial compensation. Finally, the FNE is campaigning for the removal of artificialized areas such as parking lots in commercial areas, where water runs off and does not enter the ground.
Related News :