Billions spent on flood barriers now might save city later

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NEW YORK — 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 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.”

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.

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