Protecting The Netherlands' Vulnerable Coasts With A 'Sand Motor'
Along the southwestern coast of the Netherlands, not far from The Hague, kite surfers glide on the waves around a huge sand peninsula where beachcombers photograph seagulls.
But the peninsula is more than just a recreation spot. It's also an experiment in coastal management: It keeps the sea away from nearby cities.
The Dutch call it "De Zandmotor" — the Sand Motor, also known as the Sand Engine.
"We don't have a big dike here protecting us from the sea," says Joanna Scholten, a retiree from The Hague walking on the beach near the Sand Motor. "This is a good experiment because it works with nature. It protects us, and it's also a place to enjoy."
The Netherlands, a country reclaimed from the sea, is already planning for the effects of a warming planet, including sea-level rise. The Dutch, long considered masters of flood management, have gone beyond the usual sea gates, dams and dikes.
Sand dunes have protected the Dutch coast for years. But the shoreline erodes easily. Tons of sand are shipped in from the North Sea to replenish it every five years.
But that's not enough to deal with the beach erosion that will come with sea-level rise, says Jasper Fiselier, an environmental engineer with Royal HaskoningDHV, a consultancy based in Amersfoort, the Netherlands.
"That's why we decided to try the Sand Motor," he says.
The idea came from Marcel Stive, a professor of coastal engineering at the Delft University of Technology. Fiselier worked with a team of scientists who put the idea into practice. The Sand Motor cost about $81 million and used roughly 28 million cubic yards of sand dredged from the North Sea. Over the next 20 years, waves will sweep the sand into protective barriers stretching at least six miles along the coast.
"It creates wider beaches, wider beaches stimulate natural formation of dunes, and the dunes will get bigger," Fiselier says. "That will give more safety in the end."
The Sand Motor is part of Building With Nature, a public-private partnership in which researchers from the Netherlands and other countries study how to use natural processes to prevent flooding. The U.S. Army Corps of Engineers has a similar program called Engineering With Nature.
Dutch scientists are experimenting with flexible materials for dikes and planting vegetation on the sea-facing side of dikes to absorb the sea's first blows.
The idea, Fiselier says, is to make something that can be easily adjusted to the conditions of a changing climate.
"We have a lot of knowledge on how to build dikes," he says. "Dikes are built to last 50 years. But we don't know what the conditions will be like in 50 years. We need something we can adjust as we acquire more knowledge on dealing with sea-level rise and storm intensity."
Urban planners, architects and developers in the Netherlands are also working with nature as they plan housing developments that account for climate change.
"It's almost the normal thing now to do," says Marnix De Vos, an urban designer at BVR, a landscape architecture firm in Rotterdam, where rising seas are a constant concern. "Like before, it was normal to put in a street. Well, now it's also normal to make a sustainable living area that does something with the protection against [rising] water levels."
At a bare minimum, that means building with far less concrete and asphalt, so the earth can allow rainwater to soak through, says developer Maarten Janssen.
It's a philosophy American cities can also use, he says. In Kansas City, Missouri, for example, environmentalists have pushed the 10,000 Rain Gardens project, which uses native plants in lowlands to catch and hold rainwater.
"Like in Houston, obviously a fast-growing city, but there you have lots of asphalt, lots of concrete, lots of people paving their backyards," he says. "All these things count. Obviously, there are some extreme weather events, like [Hurricane] Harvey, that you can't entirely engineer for. But in lesser storms, I think preserving natural areas would really help with flooding."
Janssen also says elevating low-lying areas might also be a solution. That's where sand comes in again.
"In the Middle Ages, before we had these big systems of sea defenses, Dutch villages in the north were constructed on mounds packed with peat, soil, even animal excrement," he says. "Today, we can elevate low-lying areas with sand."
Janssen and De Vos teamed up with the Rotterdam architecture firm ZUS to test-build a neighborhood elevated by artificial sand dunes.
The result is Duin (Dutch for "dune"), a new neighborhood near Almere, a suburb of Amsterdam and about an hour's drive east of the Sand Motor.
Almere is in Flevoland, a province reclaimed in the 1960s after construction of a sea wall. The land used to be submerged beneath an inland sea, the Zuiderzee, which, after land reclamation, has shrunk to a lake.
"It was kind of the big farm field of Holland," says Jos Hartmann, a ZUS architect. "You had super-nutrient-rich agricultural land. You had a lot of space."
The Duin neighborhood is close to the local dike. Hartmann gives me a tour. We walk on paths made of seashells, past sandstone-colored homes with wooden wind chimes.
We're surrounded by sandy hills flecked with sprouts of sea grass. These dunes were created with 3.3 million cubic yards of sand dredged from a nearby lake — the remains of the Zuiderzee.
The dunes elevate the homes by up to 30 feet, which means Marion Voigt, a Fed Ex manager who lives here with her two kids, can see over the dike and enjoy views of the lake.
"It looks like you're in a vacation resort," she says, laughing. "My kids, they're seven and 12, and they play football in the sand. When there's a rainstorm, the sand absorbs the water, so no flooding in the streets."
The sand has an added benefit. It not only absorbs rainwater. It can also purify it.
Hartman, the ZUS architect, points out that half the Dutch water supply is already filtered by sand dunes.
"We are always thinking of new ways to keep our feet dry," he says. "The best solutions are ones that have many uses and benefits."
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