How to fight a rising sea
What the Netherlands has done – and is urgently planning to do – in the face of climate-driven sea-level rise holds important lessons for the rest of the world.
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Besides global warming, scientists say the challenges these regions face have other causes as well. Levees, sea walls, drainage canals, dams, and other land-use patterns have taken a toll. Deltas tend to subside (sink) naturally, accentuating the rise in sea level. Past engineering projects can actually limit the ability of natural processes to replenish the land mass of deltas.Skip to next paragraph
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A patch of the Netherlands between Rotterdam and Gouda, called Zuidplaspolder, highlights the issue in a way that New Orleans might recognize. The 19-square-mile area is bounded by dikes and the Gouwe River. Face the river, and the landscape looks like a typical river plain. But turn and face Zuidplaspolder, and you see a steep decline dropping more than 20 feet. The huge dimple in the delta stretches as far as the eye can see.
It's the lowest spot in Europe, some 23 feet below sea level.
"And it's all subsidence," says Willemien Croes, a planner with the provincial government of South Holland. Over the centuries, residents dug up thick layers of peat to warm their homes in Gouda, Rotterdam, and Amsterdam, she says. Much of Zuidplaspolder then filled with water. Farmers pumped it dry, grew crops, and raised dairy herds on the rich clay and peat. When the soil settled, farmers ringed the area with dikes for protection.
The area's low elevation and the anticipated increased future risk of floods, combined with development pressures from Rotterdam and Gouda, have turned this area into one of the country's biggest adaptation challenges. But it's hardly alone: Some 60 percent of the country, accounting for 70 percent of its gross domestic product, lies below sea level.
These sinking lowlands are protected along the coast by sand dunes, dikes, and sea barriers that stretch across the mouths of estuaries. These natural and engineered defenses have protected millions from the North Sea since a devastating storm surge hit the country in 1953. But these defenses have come at an ecological cost. Unlike river deltas such as the Mississippi's, which grew as sediment washed downriver from deep in the North American interior, the Dutch delta was built by the sea. Currents swirling through the Strait of Dover since the end of the last ice age eroded the white cliffs and deposited the material along the Dutch coast.
That process has slowed substantially, says van Winden, who works for Stroming, an environmental consulting firm in Nijmegen. Although the delta drains three of Europe's major rivers – the Rhine, Meuse, and Scheldt – the rivers never carried enough sediment to build the delta, and don't carry enough silt to maintain it today. From that standpoint, he says, over the long term "we are living beyond our means."
Dutch humble in face of rising threat
Faced with the twin threats of increased river flooding from inland storms and higher ocean storm surges as the climate warms and sea levels rise, the country aims to meet these challenges with a variety of approaches, ranging from complex engineering to "natural." But it's doing so with increased humility, given the levee failures in New Orleans after hurricane Katrina in 2005.
"If you want a caricature of the Netherlands, it's: 'We have the dikes; we are 100 percent safe. So just go on with your life,' " says Pieter Bloemen, who runs the government's Adaptation Program for Spatial Planning and Climate. But these days, "even we proud Dutch, with climate change in the back of our heads, have to think about broken dikes. That's a big paradigm shift."