Building with Nature Project

Four pilot projects

Noorderzijlvest participated in four pilot projects as part of the Building with Nature project:

Channel management (Cross-project exploration -Wadden Sea dykes)

Rijkswaterstaat and Noorderzijlvest collaborated on the Wadden Sea Channel Management Exploratory Study. We studied the expected changes in the location of the channels and sandbanks. This was worked out for four scenarios involving various soft measures. Soft measures are measures in which we move soil from the same area, for example by dredging and dumping. One scenario adds hard material for the construction of a flow control dam.

We studied the expected effects of the four scenarios with a hydromorphological model. This is a mathematical model that indicates the influence of local changes in soil conditions on the channels and sandbanks in a wider area.

We compared the outcomes of the four scenarios with:

• The current method of protection: backfilling: with hard material such as steel slag.
• We compared the scenarios in terms of aspects such as location and currents, environmental impact, and costs.

The conclusion of the study is as follows: replacing the hard material infill with one of the four other scenarios does not result in any improvement in terms of costs or environmental impact. The long-term effect on the location and flow of channels and sandban ks is highly uncertain. Moreover, there is a high probability that we would have to repeat the measures on a regular basis. 

Rijke Dijk Delfzijl (Cross-project exploration -Wadden Sea dykes)

With the Rijke Dijk (Rich Dyke), we created a more natural transition between the dyke and the water. Dyke reinforcements along the Wadden Sea are usually carried out with asphalt surfacing. The transition between dyke and sea is therefore hard and smooth. This makes it difficult for plants and animals to grow against the dyke. And the wave run-up is not slowed down, so waves can crash far up the dyke. With a more natural transition, we are working to improve safety and give nature more room. Between Eemshaven and Delfzijl, shapes have been created at various locations between the low and high tide lines. Saltwater remains in these shapes. Plants and animals that belong in saltwater can now grow there.

Double dyke Watum (Cross-project exploration-Wadden Sea dykes)

With the Dubbele Dijk (Double Dyke), we created a brackish (salty) area behind the existing dyke. In the near future, seawater will be able to flow in and out twice a day with the tide. This will soften the separation between sea and land. We created an extra dyke behind the existing dyke. This prevents seawater from flowing further inland than the area between the dykes that has been designated for this purpose. If we expect high water at sea, we will close off the supply of seawater to the inland area as a precaution. This is how we keep it safe.

We carried out the Rijke Dijk and Dubbele Dijk at the same time as the Eemshaven-Delfzijl dyke improvement project. In 2021, the first companies started using part of the inner area. A tidal culvert will be installed in the southern part of the outer dyke. This is a pipe through which water flows twice a day at high tide. 

Preparations have begun. Implementation is planned for 2022. In the Interreg project, we have drawn up the conditions for use. Within these conditions, water safety and the operational management of users are feasible. 

Tidal lake near Noordpolderzijl

Together with Het Hogeland Council and the Groningen provincial executive, we have been searching for a solution to prevent the silting up of the channel to the harbour of Noordpolderzijl. This solution must be permanent, sustainable, and cost-effective.

For example, we studied a tidal lake as a solution. This is similar to the Wadden Sea harbours on the German coast. A tidal lake is a lake that fills up at high tide and empties at low tide. The filling and emptying of the lake could potentially prevent the channel from silting up again and again, which would then require dredging. This could also result in a smoother or more gradual transition between freshwater and saltwater.

We conducted further research at Noordpolderzijl. This research shows that a combination of measures outside and inside the dykes could improve Noordpolderzijl in many areas. For example, for the salt marshes, reducing silting in the harbour, and softening the existing hard boundary between Wad and dyke. However, there must be sufficient support for this. We are continuing with the preparations. And we are expanding the area and the themes that we are including in the research. More information Port of Noordpolderzijl Project

International exchange of knowledge and experience

In the Building with Nature project, we exchanged knowledge and experience with all international partners. Knowledge and experience of all projects that have been carried out and in which Building with Nature (or Nature-based solutions) has been applied. Each partner has developed policy proposals. This policy makes the application of building with nature easier than the existing grey (concrete) solutions. We would like to study the issue of dyke improvement in and near Natura 2000 areas. In the coming years, this topic will be part of the Knowledge and Innovation Programme of the Flood Protection Programme (HWBP). We will identify the problems. Then we will look for solutions to the regulations that make building more difficult or prevent it unintentionally.

What is Building with Nature?

In 2017, 15 parties signed a partnership agreement for the Interreg NSR Building with Nature project. Combating flooding by using nature, rather than controlling it. That is Building with Nature (BwN). The results of the project were published in July 2021.