Benthem Crouwel Overhauls the Afsluitdijk for the Next Century

Dutch studio Benthem Crouwel has completed an eight-year overhaul of the Afsluitdijk, reinforcing the 32-kilometre dam with 75,000 interlocking concrete blocks and adding a migratory fish passage that reopens a route blocked for almost a century.

The Afsluitdijk was built between 1927 and 1932 to protect the Netherlands from North Sea storm surges and flooding. According to Benthem Crouwel, the renovation ensures the dam can now withstand a severe one-in-10,000-year storm while preserving its long, linear form.

"The Afsluitdijk is one of the Netherlands' most iconic waterworks and a landmark of Dutch water engineering," studio partner Daniel Jongtien told Dezeen.

"The significance of the Afsluitdijk is huge on many levels. It was built in the 1930s to close off the former Zuiderzee, creating the IJsselmeer and fundamentally changing how the country manages water," Jongtien explained. "The brief was to strengthen the iconic and monumental character of the Afsluitdijk without losing sight of its primary function."

With a quarter of the country below sea level, marine engineering infrastructure is a common sight across the Netherlands. The Afsluitdijk is among the most notable examples, separating the IJsselmeer lake from the Wadden Sea.

Benthem Crouwel has developed the renovation since 2018 with construction company BAM and contractor Van Oord, alongside investors Rebel and Invesis. The group will maintain and oversee the project for 25 years.

The studio reinforced the entire length of the structure with 75,000 interlocking Levvel-blocs and raised it by two metres. The blocks sit in a deliberately symmetrical, regular pattern with rough surfaces designed to allow marine vegetation to latch on.

The team also added pumping stations, discharge sluices, storm surge barriers, the fish passage and a cycle path. Benthem Crouwel said its goal was simplicity, with visible elements intended to "reveal how the infrastructure works and enhances the experience of the Afsluitdijk".

"The design is characterised by spectacular simplicity – abstract in form and minimalist in detail," said Jongtien.

"The architecture is restrained, allowing the function of the dike to remain visible while supporting technology is kept out of sight," he continued. "At the same time, where elements are made visible, they have a clear functional and architectural purpose."

Six pumping stations, housed in four-metre-high domes, count among the few deliberately visible architectural additions. The pumps discharge excess water from the IJsselmeer into the Wadden Sea.

"The almost 12-metre-high pumps beneath them discharge 275,000 litres of water per second, comparable to filling an Olympic swimming pool in nine seconds," the studio said.

A 15-metre-wide opening carved into the structure gives fish a new passage between the IJsselmeer and the Wadden Sea, reinstating a migratory zone between salt and fresh water that the dam had blocked since its construction.

"It represents a shift in thinking: from simply keeping water out to balancing flood protection with ecological connectivity," said Jongtien.

A new cycle and pedestrian route runs along the Wadden Sea side, with viewpoint platforms intended to give users "a more direct experience of the scale of the Afsluitdijk". The existing route on the IJsselmeer side was retained.

The photography is by Jannes Linders.

With rising sea levels intensifying the demands on Dutch flood defences, the project points to a model in which monumental infrastructure doubles as ecological corridor and public landscape.