To control floods, the Dutch turn to nature for inspiration

Cheryl Katz in Yale Environment 360: On a freezing winter day along the south-central coast of Holland, two beachcombers, hunched against the wind, stroll along a crescent of sand extending more than half a mile into the North Sea. Nearby, a snowkiter skims over the 28 million-cubic-yard heap of dredged sediment spreading along the shore. If all goes as planned, the mound will eventually disappear, rearranged by ocean currents into a 12-mile-long buffer protecting the coastline for the next two decades.

This is the Sand Engine, one of the latest innovations from Dutch masters of flood control technology and designed, as the national water board Rijkswaterstaat says, so that “nature will take the sand to the right place for us.” After having constructed the country’s vaunted system of sea gates and dikes, Dutch planners and engineers are now augmenting it with new technology enlisting nature to keep the water at bay.

“Normally, there is a lot of erosion here,” says hydraulic engineer Mathijs van Ledden, sweeping an arm toward the snow-covered spit snaking around an elongated lagoon. Van Ledden is a flood risk reduction specialist with Royal HaskoningDHV, a Dutch engineering consultancy involved in creating the Sand Engine, currently 2.2 miles wide. “This big reservoir of sand should re-nourish the rest of the coast in time,” he says, gesturing toward the skyline of The Hague, several miles away.

The Sand Engine will fortify eroding beaches as ocean currents slowly redistribute its dredged material. The Sand Engine is the signature project of Building with Nature, a consortium of Dutch industries, universities, research institutes, and public water agencies looking to harness natural systems for next-generation hydraulic engineering. Completed in late 2011 at a cost of 50 million euros ($67 million), the Sand Engine’s goal is to provide long-term fortification for eroding beaches as ocean currents gradually redistribute its dredged material. Until now, this coastline needed sand replenishment every five years, requiring expensive dredging that damaged marine ecosystems. The Sand Engine will feed beaches for about 20 years at half the price, said Marcel Stive, chair of coastal engineering at Delft University of Technology (TU Delft) and principal creator of the technology....

A Dutch beach, shot by Albert Kok, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license