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On this anniversary of the 9/11/01 attacks from the air, some New Yorkers are worried about an even more serious threat from the sea. Today’s New York Times’s front-page headline reads “New York is Lagging as Seas and Risks Rise, Critics Warn,” and details how city officials are planning to cope with flooding of underground systems the city lives on. A year ago, Mayor Michael R. Bloomberg shut down the subway system and ordered evacuation of 370,000 people as Hurricane Irene crept north along the Atlantic coast. The hurricane weakened into a tropical storm before it hit New York and damage was limited, but nature’s warning was heard in a city with a 520-mile-long coast packed with people and buildings. Irene’s storm surge came within a foot of paralyzing transportation in and out of Manhattan, according to Klaus H. Jacob of Columbia University’s Earth Institute, who added that the “most vulnerable systems, like the subway tunnels under the Harlem and East Rivers, would have been unusable for nearly a month, or longer, at an economic cost of about $55 billion.”
New York City’s core problem is that the world ocean is rising, and rising faster and faster. The Environmental Protection Agency put it this way in 2010: “After a period of approximately 2,000 years of little change, average sea levels rose worldwide throughout the 20th century, and the rate of change has accelerated in recent years. … When averaged over all the world’s oceans, absolute sea level increased at an average rate of 0.06 inches per year from 1870 to 2008 … From 1993 to 2008, however, average sea level rose at a rate of 0.11 to 0.13 inches per year—roughly twice as fast as the long-term trend.” Seas will continue rising for the indefinite future, with the speed of change depending on many variables, such as how much the ocean will expand as global warming heats sea water and how quickly Antarctic and Greenland ice caps melt and flow into oceans. Projections assuming continued accelerating loss of polar ice give about a two-foot higher ocean by 2050.
So what will resourceful New Yorkers do? One option is installing moveable sea barriers (similar to the Venice MOSE Project mobile flood barriers) under the Verrazano-Narrows Bridge, at the upper end of the East River, and between Staten Island and New Jersey. Such barriers would be expensive and might impose important collateral damages by interfering with existing water flows. For subways, authorities are considering more powerful water pumps at stations, higher entrances and floodgates to prevent water from flowing onto subway tracks. The electric company may change to submersible switches and put its high-voltage transformers above ground. City agencies have completely a few measures already, like installing porous rock and grass to help absorb storm surge violence.
Meanwhile real estate developers continue their aggressive efforts to build on some of the world’s most valuable real estate, Manhattan office and apartment sites overlooking water. City officials anticipate an additional million New York City residents in the next 20 years, all dependent on the same vulnerable systems. People everywhere are hoping that climate change and rising seas will go light on their home turf, but the bet for New York seems dicey as compared to, say, Omaha.