Earl Evleth

Ideas floated for high-tech flood control

By William Broad
http://news.com.com/Ideas+floated+fo...2100-7337_3-58
50873.html


On a cold winter night in 1953, the Netherlands suffered a terrifying blow
as old dikes and seawalls gave way during a violent storm.

Flooding killed nearly 2,000 people and forced the evacuation of 70,000
others. Icy waters turned villages and farm districts into lakes dotted with
dead cows.

Ultimately, the waters destroyed more than 4,000 buildings.

Afterward, the Dutch--realizing that the disaster could have been much
worse, since half the country, including Amsterdam and Rotterdam, lies below
sea level--vowed never again.

After all, as Tjalle de Haan, a Dutch public works official, put it in an
interview last week, "Here, if something goes wrong, 10 million people can
be threatened."

So at a cost of some $8 billion over a quarter century, the nation 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.

The Dutch case is one of many in which low-lying cities and countries with
long histories of flooding have turned science, technology and raw
determination into ways of forestalling disaster.

London has built floodgates on the Thames River. Venice is doing the same on
the Adriatic.

Japan is erecting superlevees. Even Bangladesh has built concrete shelters
on stilts as emergency havens for flood victims.

Experts in the United States say the foreign projects are worth studying for
inspiration about how to rebuild New Orleans once the deadly waters of
Hurricane Katrina recede into history.

"They have something to teach us," said George Voyiadjis, head of civil and
environmental engineering at Louisiana State University. "We should
capitalize on them for building the future here."

Innovations are happening in the United States as well. California is
experimenting with "smart" levees wired with nervous systems of electronic
sensors that sound alarms if a weakening levee threatens to open a breach,
giving crews time to make emergency repairs.

"It's catching on," said William Kane, president of Kane GeoTech, a company
in Stockton, Calif., that wires levees and other large structures with
failure sensors. "There's a lot of potential for this kind of thing."

While scientists hail the power of technology to thwart destructive forces,
they note that flood control is a job for nature at least as much as for
engineers. Long before anyone built levees and floodgates, barrier islands
were serving to block dangerous storm surges. Of course, those islands often
fall victim to coastal development.

"You'll never be able to control nature," said Rafael Bras, an environmental
engineer at the Massachusetts Institute of Technology who consults on the
Venetian project. "The best way is to understand how nature works and make
it work in our favor."

The Dutch experience
In humanity's long struggle against the sea, the Dutch experience in 1953
was a grim milestone. The North Sea flood produced the kind of havoc that
became all too familiar on the Gulf Coast last week. When a crippled dike
threatened to give way and let floodwaters spill into Rotterdam, a boat
captain--like the brave little Dutch boy with the quick finger--steered his
vessel into the breach, sinking his ship and saving the city.

"We were all called upon to collect clothes and food for the disaster
victims," recalled Jelle de Boer, a Dutch high school student at the time
who is now an emeritus professor of geology at Wesleyan University. "Cows
were swimming around. They'd stand when they could, shivering and dying. It
was a terrible mess."

The reaction was intense and manifold. 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. 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," de Haan
said. "But it's not so much in relation to the gross national product. So
it's a kind of insurance."

The 1953 storm also pounded Britain. Along the Thames, flooding killed more
than 300 people, ruined farmland and frightened Londoners, whose central
city narrowly escaped disaster.

The British responded with a plan to better regulate tidal surges sweeping
up the Thames from the North Sea. Engineers designed an attractive barrier
meant to minimize interference with the river's natural flow. It went into
service in 1982 at Woolwich, about 10 miles east of central London.

Normally, its semicircular gates lie flush to the riverbed in concrete
supporting sills, creating no obstacle to river traffic. When the need
arises, the gates pivot up, rising as high as a five-story building to block
rising waters. The authorities have raised the Thames barrier more than 80
times.

In Venice, the precipitating event was a 1966 flood that caused wide damage
and economic loss. The upshot was an ambitious plan known as the Moses
Project, named after the biblical parting of the Red Sea. Its 78 gargantuan
gates would rest on the floor of the Adriatic Sea and rise when needed to
block dangerous tidal surges.

Long debate over the project's merits repeatedly delayed the start of
construction until May 2003. Opponents claim that the $4.5 billion effort
will prove ineffective while threatening to kill the fragile lagoon in which
Venice sits. In theory, the gates are to be completed by 2010.

"People fight doing things like this," said Bras, of MIT. "But when disaster
strikes you realize how important it is to think ahead."

Planners did just that in Bangladesh after a 1991 hurricane created huge
storm surges that killed more than 130,000 people. World charities helped
build hundreds of concrete shelters on stilts, which in recent storms have
saved thousands of lives.

In Japan, a continuous battle against flooding in dense urban areas has
produced an effort to develop superlevees. Unlike the customary mounds of
earth, sand and rock that hold back threatening waters, they are broad
expanses of raised land meant to resist breaks and withstand overflows.

Tech on the Sacramento
The approach being tried in California relies on a technology known as
time-domain reflectometry. It works on the same principle as radar: a pulse
of energy fired down a coaxial cable bounces back when it reaches the end or
a distortion, like a bend or crimp.

Careful measurement of the echoes traveling back along the cable can
disclose serious distortions and danger. Kane, of Kane GeoTech, has
installed such a system in the Sacramento River delta, along a levee that is
threatening to fail.

Could such a system have saved New Orleans? "It would have given them more
information," said Charles Dowding, a top expert on the technology at
Northwestern University. "The failure of a levee would have been detected."
But experts say it is still unclear whether such a warning would have been
enough to prevent the catastrophic breaches.

Bras says sensor technologies for detecting levee failure hold much promise.
But he adds that less glamorous approaches, like regular maintenance, may be
even more valuable, since prevention is always the best cure.

"We have to learn that things have to be reviewed, revised, maintained and
repaired as needed," he said. "To see a city like New Orleans suffer such
devastation--some of that was preventable."

He added that no matter how ambitious the coastal engineering, no matter how
innovative and well maintained, the systems of levees, seawalls and
floodgates were likely to suffer sporadic failures.

"Nature will throw big things at us once in a while," he said. "There's
always the possibility that nature will trump us."