How will New York keep out a rising sea? Dikes, huge sea wall, oyster beds?

During superstorm Sandy, a swollen New York Bay overflowed into Manhattan, flooding subways, tunnels, and a major power substation.

But what if the storm surge had been stopped by a five-mile-long barrier outside the harbor? Or what might have happened if New York had built marshes and oyster beds at the tip of Manhattan that had absorbed some of a storm surge's energy?

In the wake of New York's worst natural disaster in modern times, city and state officials are beginning to consider longer-term solutions to prevent a recurrence of the flooding.

"Climate change is a reality," Gov. Andrew Cuomo (D) said during one of his post-Sandy briefings. "Given the frequency of these extreme weather situations we have had, for us to sit here today and say this is a once-in-a-generation [storm] and it's not going to happen again, I think would be shortsighted."

Even before Governor Cuomo's pronouncement, Halcrow Group, a British company that works on infrastructure projects worldwide, in 2009 proposed a five-mile fixed barrier stretching from Sandy Hook, N.J., to Breezy Point in the Big Apple borough of Queens.

Meanwhile, "Rising Currents: Projects for New York's Waterfront," presented by the city's Museum of Modern Art (MoMA) two years ago, among other things asked architects to imagine new ways of using "soft" methods to cope with rising sea levels.

And New York City has had engineers examining ways to address the prospect of rising sea levels for a city with many low-lying areas.

The first step in deciding what to do should be the formation of a harbor protection commission, says Vishaan Chakrabarti, an architect and professor of real estate development at Columbia University here. "We need to include all levels of government," he says. "We need to get the right business and civic voices involved so we can get a broad consensus."

Initially, it appears that Mayor Michael Bloomberg is dubious about the idea of building dikes to hold back the sea.

"I don't think there's any practical way to build barriers in the oceans," he said on Nov. 1. "Even if you spent a fortune, it's not clear to me that you would get much value for it."

Others say New York – the financial capital of the world and home to at least 8 million people – is already very late in acting.

"The rest of the world has been doing it for about 50 years or so," says Robert Yaro, the influential head of the Regional Plan Association, an independent group that looks at ways to improve the quality of life in New York, New Jersey, and Connecticut.

1 | 2

Next