Reinforcing the Afsluitdijk to withstand increasing climate risks

The challenge: bringing a nearly 100-year-old dike up to modern standards

The Afsluitdijk has been protecting large parts of the Netherlands from North Sea since 1932. Sitting 23.8 feet above mean sea level, it consists of a 32 km tidal closure dike, 25 discharge sluices, and two sets of navigation locks.

It was an innovative design at the time – assessing the sea’s current for the placement of locks, with a curvature that accounted for the earth’s surface and a sloping stone structure designed to minimise the impact of waves.

In fact, it’s a national monument for its visionary hydraulic engineering qualities. But nearly a century later, it no longer meets the current legal standards for water safety and needs reinforcement of renovation to withstand increasing climate change hazards.

The solution: dike reinforcement and infrastructure improvements for the Afsluitdijk

Rijkswaterstaat, part of the Dutch Ministry of Infrastructure responsible for water management and public works, is working on the reinforcement of the Afsluitdijk, strengthening the dike and increasing its discharge capacity to cope with rising sea levels.

As a trusted partner of Rijkswaterstaat, Royal HaskoningDHV has been supervising the design and construction of the pump stations, sluices, road works, earth works and hydraulic works along the full 32 km of the Afsluitdijk since 2018.

We’re also supporting the project by assessing and contributing ideas and helping with designs and calculations. And we’re playing an essential role during the implementation phase, monitoring and reporting on the progress and quality of work, providing strategic guidance, and supervising the verification and validation of documents.

In 2021, Rijkswaterstaat decided that the renovation of the existing discharge sluice sections would be excluded from the contractor’s scope. In 2024, a separate consultancy contract was awarded to Royal HaskoningDHV to prepare design and tendering for the renovation of 15 of the 25 discharge sluices with revised design conditions after original assumptions were found to be inadequate.

We expect to remain involved until the project’s completion.

Associated projects and involvement

Prior to supporting Rijkswaterstaat during the project execution stage, Royal HaskoningDHV had supported a competing consortium of contractors with its tender. As part of this process, innovative revetment blocks were developed to reduce wave impacts and tested these in hydraulic laboratories. These revetment blocks have since been patented.

Our work for the contractor was greatly valued by the joint venture, despite not being awarded the contract, and resulted in one of the highest scores ever awarded in an EPC tender by Rijkswaterstaat.

Beyond reinforcing the dike, this project also provided an ideal opportunity to overhaul the A7 motorway, extend the existing large locks in the complex at Den Oever and Kornwerderzand with a storm surge gate, and implement a gate structure in the dike to cater for a fish migration river.

The result: a climate-proof dike to prevent future flooding

Once complete, the Afsluitdijk will meet the legal safety requirement of 1 in 10,000 years, protect the Netherlands against expected climate change hazards, and provide a safe and sustainable living environment for generations to come.

The newly built pumping stations will be able to pump enough water into the Wadden Sea to minimise inland flooding during extreme weather conditions – and could fill an Olympic-size swimming pool in 5 seconds.

The project will also preserve the twisted shape of the original discharge sluices’ pillars which are designed to weaken incoming waves and provide space for plants and insects which attract birds.

The planned new lock at Kornwederzand, at 25 metres wide and 140 metres long, will be able to accommodate wider and deeper vessels – delivering economic benefits for shipyards, coastal shipping companies, and fisheries.

And the fish migration river will ensure that fish can swim from salt to fresh water and vice versa to complete their lifecycle, helping to enhance biodiversity.

What’s more, comprehensive analysis and extensive tests in hydraulic engineering laboratories have resulted in two patented inventions which can be applied all over the world to create climate-proof infrastructure.