How to Keep New York Afloat ; with Sea Levels Rising, Once-a-Century Floods May Become Once-in-20- Years Events. One Solution: Huge Storm-Surge Barriers

Article excerpt

Like many New Yorkers, Radley Horton often frets about tomorrow's weather. Unlike many, it's his job. A scientist at NASA's Goddard Institute for Space Studies (GISS) and coauthor of a forthcoming study on the effects of climate change in New York City, he is particularly concerned about an often-overlooked aspect of global warming: bigger, stronger storms.

"It's not a linear relationship," he says on a subway ride to Manhattan's South Ferry station, which would be mostly underwater in a Category 2 hurricane. "A little bit warmer sea surface equals the potential for a lot stronger storm." And feeding off the greater ocean warmth, full-blown hurricanes may arrive at New York City with increasing regularity.

By 2050, stronger storms and rising sea levels may make the flood that previously hit once every 100 years a once-in-20-years event, according to GISS. With a possible three-foot sea level rise by 2100, flooding could occur every four years. "Our old ideas about climate may have to change," he says. "We need to be open to all possibilities."

Even as high-profile politicians like California Gov. Arnold Schwarzenegger and New York Gov. George Pataki pledge to reduce their states' carbon "footprint," cities like New York and London - and entire countries like the Netherlands - are moving to adapt to long-term climate change.

With slogans like, "Why should you worry about a hurricane? It's not like you live on an island" and a tripling of storm shelters since Katrina, New York City's Office of Emergency Management has prepared for at least some of the short-term possibilities.

But even before Katrina, the city's Department of Environmental Protection (DEP), which manages the city's freshwater supply and wastewater - 13,000 miles of pipe, total - formed a task force with GISS to look at the long-term effects of climate change.

Among other things, the DEP was concerned by the damage storm surges might inflict on a city surrounded by water. Although city officials declined to discuss concrete solutions for this article saying they were still in the "assessment" phase, scientists foresee potential fixes ranging from raising key infrastructure and building dikes, to flood gates and temporary seals over tunnel entrances. One group proposes raisable flood barriers large enough to protect all of Manhattan Island.

Sea levels have risen almost a foot in the past century, partly because of ice melt and thermal expansion (warmer water has more volume), and partly because of naturally occurring land subsidence of the Northeast. In the same period, area temperatures have risen nearly 2 degrees F. About two-thirds of that increase occurred in the past 30 years and sea-level rise has accelerated in the past decade. "The core body of knowledge has solidified" on climate change, says Cynthia Rosenzweig, the lead GISS scientist on the climate-change task force. "We're moving into a solution phase."

But possible solutions - and how to pay for them - are still "big question marks," says Gary Heath, director of bureau operations and environmental analysis at the DEP. Although antiflooding technologies are basic and well established, implementing them in a city as old and crowded as New York is no simple task.

Elevating roads, for example, sends more runoff into subway grates. Water pumped out of subway tunnels - already some 14 million gallons daily - goes into sewer systems that might be overtaxed by rainwater. "You solve one problem and you create another," says Madan Naik, chief structural engineer of New York City Transit. "It's got to be a collaborative effort, whatever we do."

Much of this city of 8 million, the largest and most densely populated major city in the US, is only 10 feet above sea level. The potential 30-foot storm surge accompanying a Category 3 hurricane would flood large swaths of south Brooklyn, parts of Queens, Staten Island, and Manhattan below Canal Street, including the World Trade Center site - 100 square miles total. …