What might Hurricane Sandy do to New York City? See excerpts below from my 2006 book The Ravaging Tide: Strange Weather, Future Katrinas, and the Coming Death of America’s Coastal Cities (Simon and Schuster/Free Press). It’s a depressing title meant to help shock us into preventing these worst-case scenarios from coming true via global climate change. But it might now be too late for parts of imperiled New York. As you read, keep in mind that as of Sunday night October 28th, the National Hurricane Center was forecasting that the storm could hit anywhere between Delaware and Rhode Island, with a surge tide as high as 11 feet in some places. Even if New York City avoids a direct strike, it is still facing a potentially “worst-case scenario” in terms of surge tides.

Adapted from chapters five and six of the book: The Raving Tide: Strange Weather, Future Katrinas, and the Coming Death of America’s Coastal Cities (2006, Simon and Schuster/Free Press) by Mike Tidwell

The Worst-case Scenario for New York City:

In September 1985, Hurricane Gloria steamed up the Atlantic coast and made landfall just above the mouth of New York harbor, passing north of Manhattan. As a Category 2 storm the surge tide could have been very serious indeed. But it was a relative dud, this storm, causing only minor flooding and spotty structural damage in beach communities across eastern and central Long Island. The reason? The New York area got lucky. The storm struck at low tide. It came when the ocean had conveniently lowered itself a full five feet in relation to the land, down from the high tide mark of just six hours earlier. This created perfect conditions for a “soft landing.” Had she arrived at the peak of high tide, then Gloria would have poured water across much of Long Island, inundating several subway stations, contaminating underground electrical and phone cables, and filling every basement and cellar from Canal Street south. Luck helped save America’s largest urban region from its most serious hurricane threat in a generation.

But New York City remains the great sleeping giant of hurricane disaster scenarios. So many mutually reinforcing factors point to catastrophe in America’s largest city that, in many ways, it’s even more frightening than New Orleans. “The Bobbing Apple” might be the name we use once the perfect storm arrives here.

Few hurricanes strike land this far north, of course, most drifting harmlessly out into the upper Atlantic, pushed there by strong westerly winds. But every 40-70 years, a major storm does slam into the New York City region. The great hurricane of 1821 passed right over Manhattan and basically cut the city in two, with the Hudson and East Rivers merging all the way up to Canal Street. At the Battery, shocked city dwellers watched as water rose as fast as 13 feet in one hour. Saving the city from total annihilation was the storm’s lucky arrival, like Gloria, at low tide.

Another major storm struck in 1892, then another in 1938 when the borderline Category 4 “Long Island Express” passed through the outskirts of greater New York, inflicting widespread death and destruction across New York state, New Jersey and much of New England. But that storm, 68 years ago, was the last major hurricane (Category 3 or above) to strike the New York Metropolitan region. It’s now a matter of when, not if, a big hurricane will strike again, according to meteorologists. And history says “when” is very soon.

The basic geography of New York City makes it a worst-case landing strip for any major hurricane. The city sits at the vertex of a giant right angle created by the land platform of Long Island and the northern shore of New Jersey. In the middle, looking like a huge catch basin, is New York Harbor, the gateway to the city. In the face of a major storm surge, the harbor acts as a funnel. The wall of seawater will plow into the harbor and then roar up the Hudson and East Rivers where it will become suddenly trapped. It’ll get backed into a corner with nowhere to go. Nowhere, that is, except up. In an eye blink, the runways of LaGuardia and JFK airports could be under 18 feet of water or more. Compounding matters is the fact that New York sits on an extremely shallow continental shelf which causes any surge to pile up on itself even before it reaches the city. These factors together give Gotham some of the highest storm-surge values in the United States.

It’s not just the city’s surface that will flood from a big hurricane surge tide, with almost all of lower Manhattan south of Broome Street under potentially tens of feet of water. It’s also the subsurface. Much of New York, like New Orleans, is below sea level. It’s actually underground, in fact, in the form of subway tracks, car tunnels, multi-story parking garages, basements, and utility tunnels. And in a big storm, it all floods. The city’s surge maps show that the Holland and Battery Tunnels will become totally filled with seawater in a big-hurricane surge.

An unsettling preview of things to come in New York arrived in December 1992 when a powerful nor’easter struck the city. It raised sea level at the southern tip of Manhattan by eight feet, flooded the Battery Park Tunnel with six feet of water, forced LaGuardia Airport to close, and shorted out the entire New York subway system, stranding passengers on trains and in stations (salt water conducts electricity, causing shorting, and it’s corrosive). The whole city was completely shut down, paralyzing the lives of 21 million people in the tri-state metro area – seven percent of the U.S. population. And this wasn’t even a hurricane.

What’s more, none of the hurricane forecasts described here takes into account the pre-hurricane “flood” that global warming will roll into the city. Amplified by local geological conditions, one U.S. government study predicts that up to two feet of ocean rise may occur by 2050 in New York and 3.5 feet by 2080. The next Big One could find the city already totally saturated with water around the edges, hanging on by a thread.

Finally, the same warming that raises sea level will also likely endow New York’s next Big One with much stronger winds. These winds will push still more surge water into the city. The wind itself could then blow through the city with impacts scarcely comprehensible. Many of the city’s two million trees, their roots wrapped tightly around all manner of buried telephone and electrical wires, will fall.

And that’s just at street level. A hurricane’s winds increase in force as you go up, in some cases nearly doubling in speed at 350 feet. This would deliver a super-enhanced body blow to every building in the city above 30 stories, which is to say pretty much the entire skyscraper forest of Manhattan. Who can even imagine the scene of flying glass and dislodged masonry filling the air and falling to the street everywhere from Midtown to the Financial District?

One wonders, however, if it’ll take a global warming-enhanced, long-overdue, direct-hit hurricane in New York City before the nation commits to real action on global warming.

But if that’s what it’ll take, we should prepare ourselves for what could be an economic wound and humanitarian crisis that outstrips all the images and impacts of September 11th and Katrina combined.