November 27, 2012

NYC flood protection a complex task

Many changes large and small can help, but even then some areas will be vulnerable, experts say.

By Adam Geller, The Associated Press

(Continued from page 1)

click image to enlarge

A raised ventilation grate doubles as street furniture installed to limit subway flooding from rain on Hillside Avenue in the Queens borough of New York. The raised grates were designed to deal with flooding from rain, not the deluge generated by Superstorm Sandy.

The Associated Press/Metropolitan Transportation Authority

"If you're thinking long-term," said Buss, who worked with communities along the Gulf of Mexico to build flood resilience after Hurricane Katrina, "you've got to use all the tools in your toolbox."

In the search for answers, few places may offer as many lessons as Houston's Texas Medical Center campus, which is bisected by a bayou and was swamped by intense rains in a 2001 storm.

The floods in Houston caused a blackout, inundated medical center streets with up to 9 feet of water, and forced evacuations of patients from the district's 6,900 hospital beds, some airlifted from rooftops by helicopter. The campus sustained more than $2 billion in damage.

A review of the area's flood weaknesses led officials to create a list of 112 projects, including widening the bayou and building culverts that funnel water away from the campus. But many of the projects were based on acknowledging that even if planners couldn't ensure that all the water from a future storm would stay out, they could at least work to limit the damage.

TMC's member hospitals moved their electrical vaults and backup generators out of basements to areas above flood level.

They rejiggered the way they used their space, rebuilding and moving facilities like research labs, many of which were destroyed by the flood, to higher floors.

Scores of existing buildings were fitted with flood gates, and new buildings were built surrounded by berms. Underground tunnels were outfitted with 100 submarine doors, some 12 feet tall.

The bill was $756 million, paid by the Federal Emergency Management Agency, not including millions more spent on the public works projects.

Variants of some of those flood mitigation measures could be put to work in New York, experts said, with a focus on protecting the infrastructure and centers of activity critical to its function.

SUBWAYS AND TUNNELS

Sandy exposed the weaknesses of the 108-year-old subway system, including the large number of stations in flood-prone neighborhoods and the overall porosity of a network ventilated by thousands of grates set into sidewalks.

In recent years the Metropolitan Transportation Authority, which runs the system, has begun looking for ways to defend it from water. After flooding from a 2007 storm forced closure of part of the system, the agency spent $157 million on a host of projects, including one that closed half the 1,600 grates along a low-lying avenue in Queens, raised others and installed water-activated mechanical closing devices on still more.

But those changes were designed to prevent flooding caused by rain, not storm surge, said Projjal Dutta, the MTA's director of sustainability initiatives.

While New York is designing raised entrances for a new subway line, it is far behind newer systems, like Bangkok, where most station entrances are raised several feet above street level.

ELECTRIC GRID

Widespread outages were prolonged after a 14-foot surge inundated Con Edison's 13th Street substation, swamped critical gear located just over 11 feet above sea level, and caused an explosion. Also, above-ground lines in New Jersey and New York were taken down by falling trees.

Moving or shielding key components of the electrical distribution system would alleviate such problems, but that will be more challenging in New York than in other areas of the country, said Carol J. Friedland, a civil engineer at Louisiana State University who has studied wind and flood damage.

One solution is to raise critical equipment well above sea level.

Moving more power lines below ground would offer protection from storm damage, said Roger Anderson, a Columbia University research scientist specializing in smart electrical systems. But it is very expensive. A 2009 report by the Edison Electric Institute estimated that installing lines underground in urban areas could cost up to $23 million per mile, five times the cost of lines above ground.

PROTECTING NEIGHBORHOODS

After the 9/11 terrorist attacks, some Wall Street companies sped up efforts to move their back-office operations away from lower Manhattan, protecting them by decentralizing. But most of that relocation has been done, and with the industry's strong attachment to New York, a renewed exodus is unlikely, said Mark Gibson, who leads Ernst & Young's construction and real estate advisory services practice.

That leaves it to employers, landlords and government officials to figure out how to make the area more flood-resistant. Engineers said the city could consider building an earthen berm around Battery Park. Individual building owners could investigate installing steel flood gates or fitting building openings with flood doors.

"You can't make New York City climate-proof; what you can do is make New York City more adaptable," said Cas Holloway, the city's deputy mayor for operations.

But surrendering the city's 539-mile coastline is not an option, Holloway said. "'We're not going to be pulling back or away from the water or retreating from the water," he said.

 

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