3D clay reefs should offer a more sustainable home to flora and fauna

To stop this river-bank erosion, Rijkswaterstaat uses 'tidal reefs', 3D-printed clay reefs. Combinatie Maaskracht's sustainability adviser, Esther Stapper: ‘The riverbank is located at the south-east of Oeffelt (Boxmeer). The challenge facing us is to restore the habitat of riverine plants and animals in the Meuse and along its course.’

The agreements in the European Water Framework Directive form are important starting point for this. This bank was created a few years ago as part of that challenge. Stapper: 'The bank is a so-called nature-friendly riverbank. A riverbank of this kind forms a gradual transition from water to land, that is made by shallows.'

'This is a good habitat for many plants, fish and other aquatic life. Erosion in riverbanks of this kind is a natural process. However, the process can become so serious that we must intervene. That's something we'll be doing in the near future.'

'We will be restoring the banks where there have been excessive flow slides. At the same time we will be creating defences to protect the restored bank. A few metres out from the riverside, we will form a slope to break the waves action that would otherwise erode the bank. That's how we can prevent new flow slides occurring again almost immediately.'

Open stone structure with many microclimates

'Under normal circumstances we would create a dam at the riverbank by placing rocks and stones', continues Stapper. 'The purpose of that is to break the wave action and to ensure that there is a safe habitat and spawning ground for a wide range of species. Rather than placing rocks and stones, we're now using 15 tidal reefs.’

Rotterdam based company Urban Reef developed these tidal reefs. These are made from clay using a 3D printer, and then baked in an oven to give them a ceramic finish. Stapper: ‘Other than the rocks and stones that are placed in the river, these tidal reefs are a complex network of hollows with a rough surface.'

'These hollows with rough surfaces enable all sorts of river nature to nestle in and around. They will be able to live in a sheltered environment, despite the strong current of the Meuse. That's good for biodiversity, for the ecological water quality and for the riverbank.'

'We're going to investigate and monitor this to see how well the reefs work as a dam, whether they can hold their own against the current and the conditions, and particularly whether they contribute to biodiversity. After all, the aim here is to provide a home to as many species as possible.'

The next step: making tidal reefs with materials obtained locally

The clay that is currently used to build the reefs is not from the local Maasheggen area. But that working method is the way forward, Stappen concludes. 'We are trying to make our work more sustainable on all fronts. For instance, by working towards using zero-emissions material.'

'By reusing materials which become available at high tide  and in the side channels is also part of this. The ideal future scenario is that we are able to reuse 100% of the regional available biomass and dredging spoil.'

'It is easy to imagine a future in which we can create reefs by using materials from the place where they will be located.'