The World Without Us

When Sanderson wanders through Central Park, he’s able to look beyond the half-million cubic yards of soil hauled in by its designers, Frederick Law Olmstead and Calvert Vaux, to fill in what was mostly a swampy bog surrounded by poison oak and sumac. He can trace the shoreline of the long, narrow lake that lay along what is now 59th Street, north of the Plaza Hotel, with its tidal outlet that meandered through salt marsh to the East River. From the west, he can see a pair of streams entering the lake that drained the slope of Manhattan’s major ridgeline, a deer and mountain lion trail known today as Broadway.

Eric Sanderson sees water flowing everywhere in town, much of it bubbling from underground (“which is how Spring Street got its name”). He’s identified more than 40 brooks and streams that traversed what was once a hilly, rocky island: in the Algonquin tongue of its first human occupants, the Lenni Lenape, Mannahatta referred to those now-vanished hills. When New York’s 19th-century planners imposed a grid on everything north of Greenwich Village—the jumble of original streets to the south being impossible to unsnarl—they behaved as if topography were irrelevant. Except for some massive, unmoveable schist outcrops in Central Park and at the island’s northern tip, Manhattan’s textured terrain was squashed and dumped into streambeds, then planed and leveled to receive the advancing city.

Manhattan, citca 1609, juxtaposed with Manhattan, circa 2006, showing infilling that has extended the island’s southern tip.

© YANN ARTHUS-BERTRAND/CORBIS; 3D VISUALIZATION BY MARKLEY BOYER FOR THE MANNAHATTA PROJECT/WILDLIFE CONSERVATION SOCIETY.

Later, new contours arose, this time routed through rectilinear forms and hard angles, much as the water that once sculpted the island’s land was now forced underground through a lattice of pipes. Eric Sanderson’s Mannahatta Project has plotted how closely the modern sewer system follows the old watercourses, although man-made sewer lines can’t wick away runoff as efficiently as nature. In a city that buried its rivers, he observes, “rain still falls. It has to go somewhere.”

As it happens, that will be the key to breaching Manhattan’s hard shell if nature sets about dismantling it. It would begin very quickly, with the first strike at the city’s most vulnerable spot: its underbelly.

New York City Transit’s Paul Schuber and Peter Briffa, superintendent of Hydraulics and level one maintenance supervisor of Hydraulics Emergency Response, respectively, understand perfectly how this would work. Every day, they must keep 13 million gallons of water from overpowering New York’s subway tunnels.

“That’s just the water that’s already underground,” notes Schuber.

“When it rains, the amount is . . .” Briffa shows his palms, surrendering. “It’s incalculable.”

Maybe not actually incalculable, but it doesn’t rain any less now than before the city was built. Once, Manhattan was 27 square miles of porous ground interlaced with living roots that siphoned the 47.2 inches of average annual rainfall up trees and into meadow grasses, which drank their fill and exhaled the rest back into the atmosphere. Whatever the roots didn’t take settled into the island’s water table. In places, it surfaced in lakes and marshes, with the excess draining off to the ocean via those 40 streams—which now lie trapped beneath concrete and asphalt.

Today, because there’s little soil to absorb rainfall or vegetation to transpire it, and because buildings block sunlight from evaporating it, rain collects in puddles or follows gravity down sewers—or it flows into subway vents, adding to the water already down there. Below 131st Street and Lenox Avenue, for example, a rising underground river is corroding the bottom of the A, B, C, and D subway lines. Constantly, men in reflective vests and denim rough-outs like Schuber’s and Briffa’s are clambering around beneath the city to deal with the fact that under New York, groundwater is always rising.

Whenever it rains hard, sewers clog with storm debris—the number of plastic garbage bags adrift in the world’s cities may truly exceed calculation—and the water, needing to go somewhere, plops down the nearest subway stairs. Add a nor’easter, and the surging Atlantic Ocean bangs against New York’s water table until, in places like Water Street in lower Manhattan or Yankee Stadium in the Bronx, it backs up right into the tunnels, shutting everything down until it subsides. Should the ocean continue to warm and rise even faster than the current inch per decade, at some point it simply won’t subside. Schuber and Briffa have no idea what will happen then.