Dike reinforcement Den Oever-Den Helder

The Wieringer Zeewering, Amsteldiepdijk, and Balgzanddijk protect more than 1.2 million North Holland residents from high water. In some places, they no longer meet the latest safety requirements. That is why the water board is working on reinforcing the dikes. The design is now complete and a draft project decision with an environmental impact assessment (EIA) has been drawn up. This sets out how the reinforcement will be carried out and what the consequences will be for the surrounding area.

Public Review of the Final Project Decision

The final decisions and all related documents will be available for public review from September 16, 2026, through October 29, 2026. The project decision, the project EIS (including the addendum), the approval decision, the environmental permits, and the appendices can be viewed in various ways during the public review period:

The project decision on the Den Oever–Den Helder dike reinforcement, the project EIS (including the addendum), and the appendices in theWaterschapsblad 2026, 23958 and via“Regulations on the Map”.
The environmental permits published in theProvincial Gazette under the heading “Notice of Environmental Permits for the Den Oever-Den Helder Dike Reinforcement Project Decision.”

Public review of the draft project decision

From October 24, 2025, through December 4, 2025, the draft project decision was available for public review via the Waterschapsblad (2025, 25345), via “Regels op de kaart” on the Omgevingsloket website, and in person at our office in Heerhugowaard. No comments were received.

Preview of implementation

The bidding process for the dike reinforcement is currently underway. We expect to have selected a contractor by early 2027. After that, we will work together to further develop the implementation plans. Then, construction will begin on-site. In this way, we will set the next phase of the dike reinforcement in motion, step by step.

Water safety tasks

Failure mechanism	Description of failure mechanism	Balgzanddike	Amstel Deep Dike	Wieringer Sea Defense
Inward stability (STBI)	The dike is not stable enough to withstand high water levels. This could cause parts of the dike on the landward side to slide away, causing the dike to collapse.	3.65 km
Asphalt pavement water pressure testing (ASP)	During high water, the groundwater level in the dike rises. When the water level outside the dike body drops rapidly, the water level in the dike can cause significant pressure from the inside of the dike against the bottom of the revetment. If the asphalt revetment cannot provide sufficient counterpressure, the dike will collapse.	1.60 km	2.24 km
Stone cladding (ZST)	Waves and currents can damage the different layers of set stone. When the bottom layer erodes, the dike can collapse.			3.25 km
Grass covering (GEBU)	The grass cover on the outer slope may erode due to stress from wave action or wave run-up.			0.5 km
Asphalt coating wave flaps (AKG)	Repeated wave action on the asphalt surface can cause cracks in the asphalt and lead to the collapse of the dike.			1 0.6 km

Dike reinforcement measures explained per dike

Balgzanddike

Inside

To improve the stability of the dike, a longitudinal structure will be installed on the inside (Balgzand Canal side) over a length of 3.65 km. This wall will extend 12 to 30 metre the ground and will contain regular openings to allow groundwater to flow through properly.

Exterior

The bottom edge of the existing asphalt layer will be replaced by riprap. This new covering will be 1.5 to 2.5 metre . Underneath the riprap will be layers of crushed stone, geotextile, and a thick layer of clay, which together will provide better protection against wave action and water pressure.

Amstel Deep Dike

On the Amsteldiepdijk and a section of the Balgzanddijk, kilometre outer dike revetment will be reinforced over a length of 2.24 kilometre . As with the Balgzanddijk, the lower edge of the asphalt will be removed and replaced with riprap.

Wieringer Sea Defense

On the Wieringer Zeewering, the dike reinforcement design consists of replacing the outer dike revetment in three forms: replacing riprap revetment (section 3), applying open-graded asphalt (section 4), replacing asphalt revetment (section 5).

Over a length of 3.25 km, the current riprap will be replaced by new riprap. The current riprap consists of basalt columns with a column height of 35 cm. The basalt columns will be replaced by riprap of the same column height (Basalt STS+). An ecotope layer of lava stone will be applied to the new riprap. This will create a rough surface that provides better adhesion for flora and fauna. The appearance of the dike will remain the same as it is now.

In four sections totaling approximately 500 metre , the current grass covering metre replaced by open-stone asphalt (OSA). This covering will be installed concealed: the turf and topsoil will be removed. Underneath, a layer of geotextile will be laid, topped with open-stone asphalt (OSA), and on top of the OSA, a 30 cm thick topsoil layer will be added, in which grass and herbs can grow.

The new grass layer will be sown with a herb-rich mixture, in line with HHNK's dike management policy. After the work has been completed, the dike will retain its green and natural appearance, similar to the current situation.

In two sections totaling 1.6 kilometre , the existing asphalt surface of the dike kilometre partially replaced. The top layer (wearing course) will be removed and replaced with a new layer of hydraulic asphalt concrete (WAB), which will be applied to the existing foundation. Grass concrete tiles will be placed at the transitions from asphalt to grass on the crest of the dike. These tiles have openings through which grass can grow. This provides extra strength and a natural transition to the grass covering.

Contact

Do you live in the neighbourhood the Den Oever-Den Helder dike reinforcement project, or are you involved in this area in some other way? This news page will keep you informed of the latest developments surrounding the dike reinforcement project.

For more information about this project, please contact Environmental Manager Britte Mussche at +31 (0) 72 – 582 8282, dijkversterkingdodh@hhnk.nl, or via the contact form.

Advice, reports, and memos

Notification of participation

In this dyke reinforcement project in the Noordkop, we are working in accordance with the guidelines of the Omgevingswet. That is why we published the participation notification at the start of the plan development phase (early May 2021). In this notification, we indicated how and when we will inform the local community and ask for their input, with the ultimate goal of reaching a final project decision together.

Preferred alternative

On June 23, 2020, the executive committee adopted the preferred alternative (VKA) for reinforcing this section of the dike. The most suitable solution for each section of the dike (Wieringer Zeewering, Balgzanddijk, Amsteldiepdijk) is now known and can be worked out in more detail.

Overview map showing locations for dyke reinforcement between Den Oever and Den Helder

What's going on?

On the outside of all three dike sections, the revetment, consisting of riprap, asphalt, and grass, is inadequate in large areas. And along the Balgzand Canal, the dike is not stable enough on the inside in certain sections.

What does the VKA look like?

During the exploratory phase, we worked with the local community to examine a large number of different possible solutions for all three dikes. The VKA consists of:

We are reinforcing the outer revetment on various sections of the three dike sections. This involves asphalt, grass, and riprap revetment.
On certain sections of the Balgzanddijk, we are reinforcing the inner toe of the dike by filling it with gravel.

Between 2017 and 2019, we organized several dike evenings (meetings) for stakeholders, local residents, and other interested parties. During these meetings, we presented possible solutions for the dike reinforcement, among other things. We also provided feedback on questions and wishes that we had gathered from the local community. In the fall of 2019, we presented our preliminary choice for the preferred alternative. The executive committee adopted the preferred alternative on June 23, 2020. The preferred alternative was designed in collaboration with the local community.

Working on a project decision

At the end of the planning phase, the board will lay down the design for the dike reinforcement in a project decision. This decision must be approved by the Provincial Executive of North Holland.

Why a notification?

The next phase of the project, the plan development phase, started in 2021 and will end with a project plan/project decision. In this phase, we will work with the local community to develop and design the preferred alternative (VKA). This phase will determine what the dike will look like after reinforcement. This phase will also examine which opportunities for linkage can be implemented. The purpose of this announcement is to inform you about participation during the plan development phase. View the full notification.

More information about the dike sections

Wieringer Sea Defense

The Wieringer Zeewering is the section of dike that runs from Den Oever to the Amstelmeer and is over 10 kilometre . The dike is directly exposed to the Wadden Sea. The hinterland is the former island of Wieringen and is mainly rural in nature. The foreland is the Wadden Sea, an area of high natural value. Places such as Den Oever and Hippolytushoef are located along the dike.

Amsteldiepdijk and Balgzanddijk

The Amsteldiepdijk connects to the Wieringer Zeewering and runs to the Van Ewijcksluis. The Balgzanddijk is an extension of this and continues to the sluice at Oostoever.

The dikes are enclosed by water on both sides, with the Wadden Sea on the outside. The Amsteldiepdijk was constructed in 1924 as a pilot project for the Afsluitdijk, creating the Amstelmeer on the inside. On the inside of the Balgzanddijk is the Balgzandkanaal, an important drainage canal for the water board. In some places there is a foreland barrier, a small dike in front of the dike in the sea. The Amsteldiepdijk and the Balgzanddijk are together approximately 10 kilometre .

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