Managed by Voies navigables de France (VNF), a member of the Seine-Scheldt EEIG, the Croissy-sur-Seine dyke (Yvelines) maintains a difference in water level between the two arms of the Seine and, like the Chatou and Bougival dams, guarantees navigation and the various uses of water (drinking water, industry, irrigation, leisure, etc.).
Weathered by time and the river, the dyke has undergone several erosions. The risk is the creation of hydraulic breaches, particularly during periods of flooding and ebbing of the Seine, which might result in a drop in water level of up to 3 metres over a 30-kilometre stretch upstream, thus having a major impact on the many uses of the Seine.
After an initial phase of tree felling in March 2023, under the supervision of an arboricultural expert (see our article published in April), the installation of riprap began on 3 July on the downstream section of the dyke and will last until December 2023. After a new phase of tree felling in autumn 2023, a 2nd reinforcement worksite phase will occur in 2024 on the upstream section of the dyke. This rockfill work carried out entirely from barges on the river, will reinforce 680 metres of the dike’s entire flank and guarantee its long-term stability.
The project is worth €13.6m (€13.2m of works, €400,000 of studies) and is funded by the European Union (Connecting Europe Facility), as part of the Seine-Scheldt wide-gauge inland waterway network (€3.9m) and the Île-de-France Region (€1.1m).
In 2023, in addition to the Croissy dyke, around ten major operations within the Seine-Scheldt network are being carried out on the structures of the downstream Seine, with financial support from the EU:
-renovation of the Poses and Port-Mort dams (Eure)
-the lengthening and renovation of the locks at Méricourt (Yvelines),
– renovation of the civil engineering of the Andrésy dam (Yvelines)
-renovation and modernisation of the Bougival locks (Yvelines)
– improving the reliability of the dams at Suresnes (Hauts-de-Seine)
– laying fibre optics along the Seine between Bougival (Yvelines) and Amfreville-sous-les-Monts (Eure) to enable remote control of the locks along the route.