Home' Technology Review : July August 2007 Contents 54 FEATURE STORY
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Krimpener waard." Pump-house engineer Harry Berkouwer,
whose family has lived for more than 600 years in the hamlet
of Berkenwoude (its name means "birch forest"; his means
"birch cutter"), beams when he speaks of the event.
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 pains-
taking work for engineers like Arthur Mynett, director of
research and development at Delft Hydraulics and an engi-
neering professor at the Delft University of Technology.
His group is probing for potential failure points in exist-
ing 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 e ect on the prob-
ability that others will go. Some might have a higher, oth-
ers might have a lower probability. It is not that trivial to
nd 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 e ort, let s say, that you can even use it all."
But his group is making progress; it is now r unning
simulations to show how oodwater could cascade from
polder to polder, farm to farm, and street to street under
various failure scenarios. Nathalie Asselman, a sta hydrolo-
gist at Delft Hydraulics, gave me a demonstration with a few
clicks of a mouse. On her computer ashed a map of the
city of Rotterdam. She ran a recently created model of two
possible disasters. In the rst, a major levee failed, and blue,
representing water, rapidly lled an empty area impounded
by a second levee. From there, various shades of blue---indi-
cating di erent 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 stor m-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 ooding as high as three meters in some areas.
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 ood 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 ooding, 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 trans xed by the
destr uction 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."
Modeling the Rhine
Pinpointing weaknesses in existing water barriers is just a
rst step toward understanding the Netherlands ood risk.
Rising sea level is, of course, the elephant in the room. But
for the moment, the elephant is moving slowly enough to
rank lower on the list of Dutch concerns than certain near-
term threats. One is that the Rhine could burst its banks
in areas such as Rotterdam. And as peat decomposes, land
is sinking faster than the sea is rising. (To make matters
worse, peat decomposition, triggered by centuries of Dutch
land drainage, throws o greenhouse gases.) Finally, new
roads and developments could increase runo , and popula-
tion growth could put more people in the path of disaster.
At Wageningen University s Alterra research institute,
20 earth scientists and climate scientists are trying, among
other things, to develop an accurate way of forecasting the
water level of the Rhine. The goal is to understand the entire
river as a system, from its headwaters in the Swiss Alps,
through Germany, and nally through Rotterdam to the
North Sea---to gure out how much precipitation it receives,
what hydrological processes shape it and its watershed, and
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.
Risk of breaches
faced by dike zones
(estimate ca. 1960)
■ 1/10,000 per year
■ 1/4,000 per year
■ 1/2,000 per year
■ 1/1,250 per year
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