Boskalis Nederland has begun constructing a four-kilometre tidal fish migration river through the Afsluitdijk in the Netherlands, using marine and land-based equipment near Kornwerderzand.
The meandering channel will connect the Wadden Sea with the IJsselmeer, allowing 12 target species to move between salt water and fresh water. Among them are salmon, sea trout, river lamprey, eel and sea lamprey.
The active construction spread comprises the crane vessel Aquilla alongside the transshipment pontoon Zeeleeuw, supported by dump trucks, wheel loaders and other land-based equipment.
The river is being built west of the drainage locks at Kornwerderzand. Fresh water flowing from the IJsselmeer into the Wadden Sea through the Lorentz locks creates a signal that attracts migratory fish to the area.
The Afsluitdijk blocks their route, while currents near the drainage locks can be too strong for many fish to pass. The new river will connect with deep channels on both sides of the dike and follow tidal movements in the Wadden Sea.
Changing flow rates along the route will create a gradual transition between salt and fresh water. Gates at the opening through the dike will close during extreme high tides to maintain flood protection for the surrounding area.
The wider Fish Migration River project began in 2019 following several years of preparation. Rijkswaterstaat completed the passage through the Afsluitdijk in 2023, while the Province of Fryslân is overseeing the remaining river works on both sides.
Boskalis is the main contractor for the river. Construction consortium Levvel, comprising BAM, Van Oord and Rebel, created the passage through the dike. IJsselmeerwerken VOF is shaping the contours on either side.
Construction uses rubble from the Afsluitdijk reinforcement program, sand from the Kornwerderzand navigation channel and IJsselmeer, soil from nearby road and dike works, and reed transplanted from Makkumer Noordwaard.
The project has an estimated cost of €80 million. Its initiators include Waddenvereniging, It Fryske Gea, Sportvisserij Nederland, NetVISwerk and the Het Blauwe Hart Natuurlijk coalition.
The first fish are expected to pass through the river in early 2027. The project team will then monitor fish behavior and the performance of the channel, making adjustments where required. The route will also serve as a research facility for studying migratory fish in the Wadden Sea area.
