Netherlands' 32km Afsluitdijk reopens higher, stronger, with fish river
The 32-kilometre Afsluitdijk in the Netherlands has completed an eight-year overhaul that made it higher, stronger and passable for fish and bicycles.
Architecture studio Benthem Crouwel developed the scheme since 2018 with builders BAM and Van Oord, alongside investors Rebel and Invesis, which will maintain and oversee it for 25 years. The work was designed to bring the dam up to current safety standards and improve resilience to extreme weather and rising sea levels. Dezeen
The dam was built between 1927 and 1932 to protect the country from North Sea storm surges and flooding. A storm surge is a wall of sea water pushed ashore by a storm. The Afsluitdijk separates the IJsselmeer lake from the Wadden Sea, the tidal shallows off the northern Dutch coast.
It is higher now. Workers reinforced its full length with 75,000 interlocking concrete blocks known as Levvel-blocs and raised it by two metres. Benthem Crouwel states the renewed dam can withstand a severe one-in-10,000-year storm.
The project added pumping stations, discharge sluices, storm surge barriers, a fish passage and a cycle path. Sluices are gates that let excess water drain out, while barriers close to block the sea in a storm. The new cycle route runs on the sea side of the dam, and six large domes were placed along its length during construction. Benthem Crouwel
Fish can pass through. The headline for nature lovers is the Fish Migration River, a four-kilometre tidal channel cut through the dam. It lets fish swim between salt water in the Wadden Sea and fresh water in the IJsselmeer. Rijkswaterstaat
Contractor Boskalis started building that channel, and Van Oord said on 10 September 2025 that its share of the work on the river was successfully completed. The river work sits inside the larger dam strengthening, which took place over the last eight years. Baird Maritime
Earlier project material also described the Afsluitdijk as an energy test site and included an update to the Dudok monument, the small memorial structure linked to the dam’s original construction era.
What makes this stand out for visitors is the mix of uses. You can ride the full length with the sea on one side and the lake on the other. Beneath you, fish are making the same crossing. It is flood defence you can cycle over.
