Reef blocks in the Nieuwe Waterweg present opportunities for biodiversity and water safety

These show that the reef blocks provide protection from wave energy and erosion, while also boosting biodiversity. In other words, this is a project in which water safety and nature recovery go hand in hand.

Solid collaboration

Solid collaboration between a number of parties is to thank for the success of the project.

Sustainable start-up Reefy designed the reef blocks. Rijkswaterstaat endorses the importance of nature-inclusive infrastructure in the Nieuwe Waterweg. Boskalis, which has plenty experience with hydraulic engineering and coastal defences, installed the blocks. The City of Rotterdam created space for innovation and monitoring that made collection of ecological data possible.

Backbone of living reef

The reef blocks, installed in 2023, form the backbone of a living reef. The robust blocks are 3 m long and each weigh 6 tonnes. They were designed to resist high wave forces and create a rich underwater landscape. This design has been shown to work by the ecological and technological results of the study.

Reef blocks are bringing life back into the Nieuwe Waterweg, and adding to species diversity, cleaner water and more vigorous nature. The blocks can also withstand heavy storms, break waves and protect the shore.

Ecological results

A dip into the ecological results reveals that the reef blocks tripled biodiversity, compared with normal concrete. Tunnels, passages casting shadow and rough surfaces worked together to build a dynamic ecosystem in which fish, crabs and shrimp can prosper.

The reef also provides good hiding places for such species. Other than that, the rough surfaces appear to stimulate the growth of shells and algae.

Technological results

Among other things, the technological results demonstrate that the reef blocks protect shorelines and remain stable in heavy storms, such as Storm Poly in July 2023. The reef blocks also break up waves.

The reduction in wave energy helps to silt up the reef. In turn, the silt is beneficial to coastal protection and control of erosion.

'Rijkswaterstaat highly values hydraulic engineering innovations that contribute to ecological recovery,' says Ehsan Nouzari, Water Framework Directive Environmental Manager at Rijkswaterstaat.

'Smooth collaboration between the parties and real motivation from all concerned mean that we have been able to convert the desire to innovate into a successful pilot scheme. The lessons we've learnt offer opportunities for the future.'