Future dikes

Species-rich dikes that will provide better protection, also in the future

(Photo: Karsten Russ)

In an effort to meet new safety standards, 1,500 kilometres of Dutch dikes will need to be strengthened over the next few years. This is a huge task, but it is also a great opportunity. After all, why wouldn’t you seize the chance to not only strengthen the dike, but also improve it in terms of biodiversity and make it more attractive? This is exactly what Hans de Kroon and Eric Visser aim to achieve in their Future Dikes research project.

This research is supported by the Radboud Fund.

A vision of species-rich dikes
The Future Dikes project examines the way in which a species-rich grass covering can be used to strengthen Dutch dikes.

Previous research has revealed that a biodiverse grass turf is highly resistant to the erosive effect of water overflow. As a rule, herbs tend to root deeper than grasses, and the blend of shallow and deep roots creates a solid root mat that holds the dike’s soil layers together. This means that the diverse vegetation provides an excellent first layer of protection both above and below ground. The results can be seen within a few years, as bluebells, the Great Centaury, wild marjoram and countless other herbs begin to bloom again on the dikes along the Rhine River. And dozens of wild bee species have also been counted again. Hans de Kroon: “Our research has shown that all of these grasses and herbs are working together below the ground. This results in stronger cross-linking and root anchoring, which is crucial for the erosion resistance of the dike.” (Source: voxweb)

In addition to this, a species-rich grass covering can help to restore biodiversity: this provides a setting for rare plant and insect species. Hans de Kroon: “Sowing a species-rich grass mixture on the dikes would be a huge gain for biodiversity. The dikes that meander through the Dutch landscape could therefore become a connecting factor between different ecosystems.” A species-rich vegetation complies with the Green Deal Infranature that a number of water boards signed in order to guarantee the biodiversity and environmentally friendly management of the dikes.

“Strong dikes, biodiverse vegetation and happy insects, with the added bonus of a dike that’s visually appealing. Simply put, this is a win-win situation!” - Hans de Kroon

Further research is needed to enable the large-scale application of a species-rich grass covering. More knowledge is required about the design of new dikes, and about how floral dikes can be optimally developed, maintained and restored.