Building with Nature Project

Four pilot projects

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

Channel management (POV-Wadden Sea dikes)

Rijkswaterstaat and Noorderzijlvest collaborated on the Wadden Sea Channel Management Exploration. We investigated 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 investigated the expected effects of the four scenarios using 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 shoals is highly uncertain. Moreover, there is a high probability that we would then have to repeat the measures on a regular basis. 

Rijke Dijk near Delfzijl (POV-Wadden Sea dikes)

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

Double dike at Watum (POV-Wadden Sea dikes)

With the Double Dike, we have created a saline (salty) area behind the existing dike. 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 have built an extra dike behind the existing dike. This prevents seawater from flowing further inland than the area between the dikes that has been designated for this purpose. If we expect high tides 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 constructed the Rijke Dijk and Dubbele Dijk at the same time as the Eemshaven-Delfzijl dike 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 dike. 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, both water safety and the operational management of users are feasible. More information: www.hwbp.nl/kennisbank/pov-waddenzeedijken.
 

Spoelzee near Noordpolderzijl

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

We have therefore investigated a tidal lake as a solution. This is similar to the Wadden Sea harbors 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, and the need to dredge it again. This could also make the separation between fresh and salt water gentler or more gradual.

We conducted further research at Noordpolderzijl. This research shows that a combination of measures outside and inside the dykes could improve many aspects of Noordpolderzijl. For example, the salt marshes, the reduction of silting in the harbor, and the softening of the existing hard boundary between the mudflats, the dykes, and the inner dykes. 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 Project Port of Noordpolderzijl

International exchange of knowledge and experience

In the Building with Nature project, we exchanged knowledge and experience with all international partners. Knowledge and experience about 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 gray (concrete) solutions. We would like to investigate 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 Program of the Flood Protection Program (HWBP). We will identify the problems. Then we will look for solutions to the rules that make building more difficult or prevent it without us wanting that.

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.