Flood-proofing New York City with storm barriers

who began discussing the idea several years ago with Stony Brook University oceanography professor Malcolm Bowman.

Warnings that New Orleans faced disaster from a major hurricane proved painfully true, they note, when Katrina struck in August 2005. The storm breached levees, flooded most of the city, and killed more than 1,500 people in New Orleans and elsewhere.

The next year, former National Hurricane Center director Max Mayfield told a congressional committee that “it is not a question of if a major hurricane will strike the New York area, but when.”

The city has been hit before, including by a September 1821 hurricane that raised tides by thirteen feet in an hour and flooded all of Manhattan south of Canal Street — an area that now includes the U.S. financial capital. Depending on its track, a Category 3 storm — with sustained winds of 111 to 130 mph, akin to a 1938 hurricane that swept through nearby Long Island — could produce a storm surge as high as twenty-five feet in some parts of the city. Officials estimate as many as 600,000 people’s homes could be flooded, and three million would have to evacuate because of flooding and other perils; economic loss estimates top $100 billion.

Forecasters expect a fairly average hurricane season this year. Note that the year’s first tropical depression, a potential precursor to a tropical storm or hurricane, formed Thursday, before the season even officially began. It was not expected to threaten land.

Unfortunately for NYC, hurricanes are not the only flood threat. Nor’easters also have caused storm-surge problems in the city, and scientists have projected that the waters around the city could rise by two feet or more in the coming decades because of global warming, making coastal flooding more frequent.

Hill says that a set of barriers a mile long or less at three critical points could protect fifty square miles of the city and New Jersey, according to Hill. The locations: the Narrows, the gateway to New York Harbor near the Verrazano-Narrows Bridge; the northern end of the East River, where it meets Long Island Sound; and the southern end of the Arthur Kill, a waterway between Staten Island and New Jersey.

Barriers at these locations would shield Manhattan and parts of the four outer boroughs but still leave large, low-lying areas exposed, especially in Brooklyn and Queens.

An alternative idea — for a single, 5-mile-long barrier between Sandy Hook, New Jersey, and the Rockaway Peninsula