Could a surge-protection barrier have saved New York City from much of the flood ravages of superstorm Sandy?
Malcolm Bowman and other hydrologists are convinced it could have.
Bowman, an oceanographer who has spent much of a 40-year career warily watching the tidal flows in and around New York Harbor, recalls being on the construction site of Manhattan's South Ferry subway station a few years ago.
"It was just a concrete box underground then," said Bowman,, then an observer filming a documentary. He looked up a long stairway leading to blue sky and asked a construction official, "Would you mind telling us how far above sea level is the entrance there at street level?"
Eleven feet, the official said — an elevation designed withstand possible floods from a storm that occurs once in 100 years.
"I said, 'That sounds awfully low to me and, by the way, that storm could come next week,' " said Bowman, a professor at the Marine Sciences Research Center of State University of New York at Stony Brook, Long Island.
The South Ferry station, a $530 million jewel in New York's subway system, opened in March 2009. On Oct. 29, Hurricane Sandy slammed into the New York metropolitan area, bringing a record storm surge of 13.88 feet into Battery Park, which abuts South Ferry. The station flooded floor to ceiling, destroying equipment and turning escalator wells and tunnels into caverns deep enough to scuba dive in.
Sandy's relentless, wind-driven tides inundated seven subway tunnels under the East River, immersed electrical substations, and shut down the financial district and power south of 35th Street. It flooded parts of all five boroughs in the city of 8 million and killed more than 100 people in the United States, 42 in New York City.
Bowman says a storm surge barrier to slow and disperse Sandy's floodwaters could have mitigated much of Manhattan's flooding. He's not alone.
A 2009 engineering study by Mahwah, N.J.- based HydroQual estimated that a barrier system involving massive floodgates at key points such as the East River and the Verrazano Narrows would reduce the flooded area of the New York metropolitan region by 25 percent, the population affected by 20 percent, submerged property 35 percent, and cut storm damage to sewage plants and other hazardous waste facilities by half. Conceptual designs of several such systems were floated at a 2009 conference at the Polytechnic Institute of New York University.
While such a system is expensive — estimates range to $17 billion — Sandy's damage and economic losses to the region may reach $50 billion, $33 billion of that in New York state alone, Gov. Andrew Cuomo, D, said Sunday at a news briefing. That's comparable with the $15 billion the federal government spent to rebuild New Orleans levees after Hurricane Katrina in 2005.
With most scientists suggesting climate change is increasing the frequency of such storms, the cost-benefit ratio of building a surge-protection system may make sense.
"Think about it this way," said Bowman. "Including Hurricane Irene last year, we've had two 100-year storms in two years."
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The experiences of London, St. Petersburg, Russia, and Venice, Italy, each of which built such projects, show the systems can protect dense urban populations and infrastructure. In August, new levees kept New Orleans dry from Hurricane Isaac's flooding.
"This is all proven technology," says Jeroen Aerts, a water risk-management expert with the Institute for Environmental Studies in Amsterdam who is developing estimates on strategies for averting future floods for New York City's Office of Long-Term Planning and Sustainability.
The question is money, political will and a general skepticism in some quarters, including the office of Mayor Michael Bloomberg, that big engineering solutions are the answer.
"I don't know that it is practical to put barriers," Bloomberg said Nov. 4. "It would be very difficult and very expensive just to do it for New York Harbor. You'd have to do it for Long Island Sound where a lot of the water comes down."
Cuomo says that a levee system or storm-surge barriers ought to be considered.
"The construction of this city did not anticipate these kinds of situations," Cuomo said in an Oct. 30 radio interview on WGDJ in Albany. "We are only a few feet above sea level.
"As soon as you breach the sides of Manhattan, you now have a whole infrastructure under the city that fills: the subway system, the foundations for buildings."
"It may be possible to mitigate and maybe control" future surges, said Rep. Jerrold Nadler, D-N.Y., who serves on the House Committee on Transportation and Infrastructure, but "we won't know until we carefully study it."
Preliminary estimates are $10 billion and $17 billion to undertake some combination of surge-barrier system, Aerts said. Building levees, restoring wetlands and strengthening beaches to improve the efficiency of the storm barrier would add $10 billion to $12 billion, he said.
An approach called "resilience" would probably be cheaper than barriers, he said.
"We still could leave the city open and protect the vital works like power plants and subway entrances and in addition upgrade the current building codes and flood insurance programs," Aerts said. "We are in the middle of working up estimates of both so we can then do a proper cost-benefits analysis."
This vulnerability of infrastructure is a nationwide — indeed, worldwide — issue. Along the northern Gulf of Mexico, about 2,400 miles of highways and 246 miles of freight lines are at risk of "permanent flooding" from a combination of storms and sea rise within 50 to 100 years, the National Oceanic and Atmospheric Administration said in a 2009 report. About 1,900 miles of California's roadways are vulnerable to a 100-year flood.
The hazard to humans is just as stark. A third of all Americans live in counties immediately bordering the ocean, according to a report by the U.S. Global Change Research Program, which integrates federal research on climate change. Coastal and ocean activities contribute about $1 trillion to the nation's gross domestic product. Yet half of the nation's coastal wetlands, which serve as natural surge barriers, have been lost.
A 2009 report from New York's Office of Emergency Management predicted that a catastrophic storm surge would put almost two million New Yorkers in 743,000 households and 461 miles of major roads at risk from flooding.
Bowman and other hydrologists say there are numerous ways to protect the city with surge barriers. At the 2009 conference, the concepts included a huge flap-like barrier on the East River near Long Island Sound, and a towering barrier north of the Verrazano-Narrows Bridge that would protect parts of Staten Island, Manhattan, Brooklyn and New Jersey.
The most intriguing option, according to Bowman who has seen all of these plans, is the New York- New Jersey Outer Harbor Gateway, a five-mile system of causeways and gates from Sandy Hook in New Jersey to the Rockaways in Queens. The system would deflect the energy of a storm surge and diminish water to manageable levels, according to a report by the London-based engineering firm Halcrow.
"It could have a multipurpose function," said Bowman. "It could act as a four-lane highway plus a rail connection between northern New Jersey and Long Island. It could be a very interesting New York City bypass as well as a rapid rail connection with Kennedy airport."
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There is plenty of historical precedent for storm-surge barriers. The Netherlands, where much of the country is below sea level, expanded its flood control system after a 1953 storm killed 1,836 people, according to Delta Works, the agency that runs the flood-control dams and barriers.
That led to the construction of barriers including the Maeslantkering on the waterway to Rotterdam. Completed in 1997, its two steel doors are each more than twice the length of a football field. Without such barriers, 66 percent of the country, including cities like Amsterdam and The Hague, would flood regularly, according to the Delta Works website.
Venice, Italy, is constructing 78 inflatable gates to prevent floodwaters from entering the city's lagoon. Venice has subsided as sea levels have risen, leaving it an average of nine inches lower to the Adriatic than at the start of the 20th century, according to the Ministry of Public Works.
In London, the Thames Barrier is one of the world's largest movable flood barriers, spanning 1,700 feet and meant to protect 48 square miles of central London. When raised, the main steel gates stand five stories. The gates were shut more than 100 times in their first two decades of operation, according to the British Environment Agency website, and there has been no flooding along the Thames since the barrier's 1982 completion.
A project with perhaps the closest hydrological parallels to New York City is a $6 billion barrier completed in 2011 that protects St. Petersburg, Russia, from the floodwaters of Neva Bay, the easternmost part of the Gulf of Finland. Facing semi- annual floods, city officials in the Soviet era began work on a project that includes a 15-mile-long perimeter barrier, also used as a road, and a system of gates and locks. After languishing for two decades, the project was restarted in 2003 with funds from the European Bank for Reconstruction and Development.
The gates kept the city from inundation in December when storms brought the fourth highest floodwaters on record, , said John Corsi, a spokesman for Halcrow, which oversaw completion of the project.
"That barrier has very similar characteristics" to the New York-New Jersey Outer Harbor Gateway, which Halcrow laid out in 2009, he said. "We think the barrier solution is applicable to the requirements of New York and therefore worth evaluating by the New York policymakers."
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James Titus, author of a federally funded assessment of rising sea levels along the Atlantic Coast, said policymakers have three choices: cede ground to the rising ocean, elevate the grade of the shore or land, or build barriers.
"While dikes and tidal gates may be the way to go, it's not the only way to go," Titus said. "The clear alternative is elevating the grade of Manhattan."
One advantage is that property owners can do it on their own. Titus, who owns a beach home on Long Beach Island, N.J., raised its level and built up the surrounding land in 2004.
Those who suffered damage from Sandy "should clearly elevate their home now as part of rebuilding," Titus said. "You don't need to wait for all the forces of government to come together to do it."
— With assistance from Henry Goldman in New York and Freeman Klopott in Albany, New York.