New York: The subway, after Sandy


NEW YORK was warned. In 2011, a year before Superstorm Sandy hit the city, Klaus Jacob, a scientist at Columbia University, warned in a report that even short-term flooding of New York’s extensive subway system could cause billions of dollars in damages and knock-on economic losses. On September 10th 2012, just over a month before Sandy hit, the New York Times published an extensive article highlighting Dr Jacob’s prediction.

Sandy unfolded much as scientists had feared. It was the second 100-year storm to hit the region in only a few years. Hurricane Irene, in 2011, produced a storm surge that came within a foot or so of flooding New York’s subways, according to Dr Jacob. Then Sandy hit, flooding subway tunnels and stations just as Dr Jacob had predicted. It took less than a week for New York’s Metropolitan Transportation Authority (MTA) to get most of the tunnels drained and most services operating again—and the agency was, generally, praised for getting the system back online so quickly. Still, some repairs, like those to the Montague Street Tunnel under the East river between Manhattan and Brooklyn, took over a year to complete. The MTA ultimately concluded that the storm resulted in some $5 billion in damage. Now the New York Times has taken a look back at what happened—and how the MTA can prevent more damage to the transport systems on which millions of business travellers and commuters rely. Here’s a highlight:

A good place to see how and why the Metropolitan Transportation Authority just barely survived Sandy last fall is the entrance to a tunnel at 148th Street and Lenox Avenue, in Central Harlem, where, just before the storm hit, a crew of carpenters built a plywood dam 8½ feet tall by about 55 feet wide. That ad hoc, low-tech, last-minute construction held the New York Harbor at bay and not only saved the city hundreds of millions of dollars, but also made it possible for the subway to come back to life as quickly as it did.


It endured, with about three inches to spare. The triumph might seem like a small one in the face of Sandy’s destruction, but it wasn’t. Here’s what it prevented from happening: After flooding the No. 3 line tracks to the south, and destroying millions of dollars worth of equipment, the Harlem River would have continued south, following Lenox Avenue to about 142nd Street, a junction where the 3 line joins the 2 line, which runs to and from the Bronx. By consulting both the Slosh maps and its own topographical maps, the transit authority determined the water would have flowed toward the Bronx, via what’s called the Harlem River-Lenox tunnel, and then east to 149th Street on the Grand Concourse. Then, in the worst case, the water would have moved through a connecting track, and like liquid moving through a Krazy Straw, the Harlem River would have flowed south through another under-river crossing, the Harlem River-Jerome tunnel, to 125th Street in Manhattan. From there, it would have flooded the downhill Lexington Avenue line — which happens to be the busiest one in the city, carrying more people every day, 1.8 million of them, than any other American subway system — to about 103rd Street, where the tracks rise, up toward Carnegie Hill.

In other words, the flooding from Sandy could have been much worse. Regardless of what they think about the origins of climate change, leaders in other major cities that are, like New York, vulnerable to serious flooding, would be wise to learn from the city’s example.