Dutch Counter-Flood Tech

Plety of cities around the world are below sea level, like New Orleans. So how do they keep the waters at bay? The Times looks at the "countries with long histories of flooding [that] have turned science, technology and raw determination into ways of forestalling disaster."dutch_rivers.jpg

After devastating floods killed nearly 2,000 people in the Netherlands, the Dutch erected a futuristic system of coastal defenses that is admired around the world today as one of the best barriers against the sea's fury - one that could withstand the kind of storm that happens only once in 10,000 years."Linking offshore islands with dams, seawalls and other structures, the Dutch erected a kind of forward defensive shield, drastically reducing the amount of vulnerable coastline. Mr. de Haan, director of the water branch of the Road and Hydraulic Engineering Institute of the Dutch Ministry of Transport, Public Works and Water Management, said the project had the effect of shortening the coast by more than 400 miles.For New Orleans, experts say, a similar forward defense would seal off Lake Pontchartrain from the Gulf of Mexico. That step would eliminate a major conduit by which hurricanes drive storm surges to the city's edge - or, as in the case of Katrina, through the barriers.The Dutch also increased the height of their dikes, which now loom as much as 40 feet above the churning sea. (In New Orleans, the tallest flood walls are about half that size.) The government also erected vast complexes of floodgates that close when the weather turns violent but remain open at other times, so saltwater can flow into estuaries, preserving their ecosystems and the livelihoods that depend on them.The Netherlands maintains large teams of inspectors and maintenance crews that safeguard the sprawling complex, which is known as Delta Works. The annual maintenance bill is about $500 million. "It's not cheap," Mr. de Haan said. "But it's not so much in relation to the gross national product. So it's a kind of insurance."
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