Room for the River

dutch-dykes

Special Series: Fast Forward

Dutch Dikes

By David Kattenburg

As Earth’s atmosphere warms, melting ice caps and thermal expansion of the oceans have caused sea levels to rise by an estimated two tenths of a meter relative to early twentieth century levels, the Intergovernmental Panel on Climate Change announced in 2013.

A more recent report in the prestigious US journal Proceedings of the National Academy of Sciences, based on satellite measurements, announced that the annual rate of sea level rise is faster than previously estimated — about 1.4 mm per year.

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Dordrechters enjoy drinks beside the Rhine

A millimeter rise in ocean levels may seem tiny, but the consequences for coastal communities around the world — and for small island states that may disappear completely by the end of the century — are huge. In response to increasingly frequent disastrous events such as Hurricane Sandy and Katrina, and major floods up and down western Europe, calls for more effective flood control designs have proliferated.

Who better to turn to for ideas than the Dutch, who’ve been staving off floods for centuries? Over the past decade, Dutch engineers have been designing innovative, nature-based flood control systems that are cheap, environmentally friendly and effective.

 

Southeast of the city of Dordrecht, near where the Rhine estuary flows into the North Sea, a new flood control system — innovative by Dutch standards — is now in place. It’s part of a program called Room for the River. In late 2015, a 23-kilometer stretch of concrete dike encircling the village of Werkendam, upstream from Dordrecht, was breached in several spots, allowing the adjacent Noordwaard Polder to flood under high river conditions, thereby lowering river levels at Dordrecht.

Mindert DeVries, on his "soft" dike near Werkendam

Mindert DeVries, on his “soft” dike near Werkendam

In its place, a much smaller dike made of clay and grass now protects Werkendam. Flanking rows of willow trees will lower wave intensity — and provide bird habitat (a national park is located a few kilometers downstream). Sheep will graze along its grassy crest.

Another novel design feature of the new dike is its gradual slope, making it largely invisible to people living behind it. It’s “unbreakable,” says Mindert de Vries, an ecologist and sediment morphologist with the Delft-based research institute Deltares.

If waters do rise high enough, they’ll spill over the top of the dike, rather than break it, says de Vries, who was involved in the dike’s design.

Rhine River Taxi

Rhine River Taxi

The icing on the cake: a clay-grass dike is cheap to build and has a smaller carbon footprint than dikes of concrete and asphalt. No wonder the design has captured attention across the Atlantic. Similar flood defense designs are now in the works in New York City, Mississippi and Louisiana.

Listen to Mindert and I as we drive through Rotterdam, down to Dordrecht, to visit his “soft” dike.

Fast Forward: Stories of Challenge & Change is produced with the generous support of the Government of Canada, the Social Justice Fund of Unifor, and the Community Radio Fund of Canada. Thanks to Roger Dumas for his wonderful human brain ‘sonifications’, one of which appears in Fast Forward intros/extros. For more information about Roger’s Pieces of Mind CD, go here.

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