Building living waterworks with nature

If it were up to Wageningen University & Research, the fight against water is to become more of a collaboration than a battle. WUR scientists, frequently in collaboration with Deltares, work to make waterworks greener. A dam or dyke can often do much more than merely protect humans from flooding when nature is involved. Through the correct approach, natural processes remain intact and may even be a solution. Building with Nature, also known as eco-engineering, revives oyster reefs, uses natural current to transport sludge and brings mangrove trees back to stop the water.

Oyster reefs against erosion

In the Netherlands, WUR researcher Brenda Walles works on oyster reefs in the Oosterschelde. The flood barrier there has caused a constant erosion of sludge and plates, causing a threat to a valuable habitat.

Placing empty oyster shells, which are kept in place by a metal construction, has created a suitable location for oyster larvae. The living oyster reef thus created grows naturally and keeps the sludge and plates in place by breaking the waves of the Oosterschelde. The weakened swell displaces less sand, conserving the unique estuary habitat. Nature's forces are used to preserve nature.

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Mangrove trees to prevent flooding

The oysters also help prevent flooding in Bangladesh. The disappearing mangrove forests have rendered the area vulnerable to extreme weather conditions and increased water levels due to climate change. WUR created oyster reefs similar to those in the Oosterschelde to keep sludge in place. This sludge forms an excellent substrate for mangrove trees, which, in turn, protect the land from flooding.

Research on the possibilities of using mangrove leaves as nutrition for shrimp, which is a source of income and food for the local community and fishers, was conducted in collaboration with the NGO Solidaridad and Khulna University. Because the intervention also offers short-term benefits, there is extra support among the Bengalese population.

In central Java, wooden dams do the oysters' work. But the principle is the same. In some areas, the coast had shrunk by as much as three kilometres after the mangroves disappeared. Over a stretch of coastline more than 20 kilometres in length, dams have been created and mangroves planted. As the trees grow, so does the coast.

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Let the current do the work

Back in the Netherlands, work is being done on salt marshes in the Wadden Sea near Harlingen. To keep the harbours accessible, they are dredged using a trailing suction hopper dredger, which spreads the sludge off the coast. Subsidies from the Wadden Fund enabled WUR scientists to test a so-called sludge motor. This is a strategy where the sea's current is used to transport the sludge to more distant salt marshes.

And with success! Dredging thus contributes to the salt marshes' growth, preventing it from disappearing below sea level. There is also more room for biodiversity in the larger marshes. They form an excellent breeding ground for birds, for example. Thus, harbours remain accessible, while nature benefits; with a little help from science.