Despite such mergers, there are still 27 separate water boards in a country that’s only about twice the size of New Jersey. And the hodgepodge of record-keeping makes painstaking work for engineers like Arthur Mynett, director of research and development at Delft Hydraulics and an engineering professor at the Delft University of Technology. His group is probing for potential failure points in existing Dutch dikes; that requires knowing the precise height and engineering characteristics of every one of them. “We are trying to integrate everything,” Mynett says. “If one of these dikes goes, collapses, that has an effect on the probability that others will go. Some might have a higher, others might have a lower probability. It is not that trivial to find out. From history, the Netherlands is a country which is also separated in rather small administrative units–not only the water boards, but municipalities and railroads. All these organizations have their own databases. It’s already quite an effort, let’s say, that you can even use it all.”
But his group is making progress; it is now running simulations to show how floodwater could cascade from polder to polder, farm to farm, and street to street under various failure scenarios. (Video of flood simulations and animations.) Nathalie Asselman, a staff hydrologist at Delft Hydraulics, gave me a demonstration with a few clicks of a mouse. On her computer flashed a map of the city of Rotterdam. She ran a recently created model of two possible disasters. In the first, a major levee failed, and blue, representing water, rapidly filled an empty area impounded by a second levee. From there, various shades of blue–indicating different depths–trickled out slowly to parts of the city, rising to a height of about a meter over several days. That would be serious, but not life-threatening or city-wrecking. Then Asselman showed what would happen if the second levee weren’t there and a major storm-surge barrier several kilometers away were left open. What unfolded would, if it happened in real life, dwarf the New Orleans catastrophe. In a matter of hours, much of Rotterdam was awash in blues, with flooding as high as three meters in some areas.
Reassessing risk: The Dutch dike system was tailored to flood probabilities calculated around 1960. Faced with climate change and population growth, the Dutch are now seeking systemic forms of protection, from upstream water impoundments to floatable buildings and roadways.
Credit: Carol Zuber-Mallison
That the Dutch haven’t previously tried to understand the consequences of calamities in such detail points to the irony of having strong defenses. No catastrophic flood has befallen the nation since 1953. That freedom from disaster has bred complacency. “Sometimes a plane falls down and you can investigate why it falls down,” says Kwadijk. “The trouble is, we never get any flooding, so you can’t test anything, and you can’t convince the public [of the danger].” But all that changed in 2005, when the Dutch were transfixed by the destruction in New Orleans following Hurricane Katrina. “Katrina raised awareness in the Netherlands,” says Mynett. “To the general public, it wasn’t, ‘Silly Americans can’t take care of water management.’ It was, ‘Oops–this can happen.’ It is more a feeling of solidarity.”