Before the flood: New York City is just beginning to gird for the ‘100-year storm,’ if it’s not already too late

Flooding at the 23rd-Ely subway station. ()
Tweet Share on Facebook Print

When Mayor Michael Bloomberg released his master plan for the city, PlaNYC, in 2007, large sections were dedicated to reducing the city's contribution to climate change: more efficient energy use, cleaner fuels, the retrofitting of old buildings; and in the years since, several initiatives have advanced that goal, like the bike-sharing program, encouragement of "white roofs," the adaptation of the harbor to move more cargo shipment to barges and trains.

All of this will significantly reduce the city's contribution to greenhouse gas emissions and climate change in the future.

What all of this won't do—can't do—is reverse what may be very real dangers the city faces as a result of environmental changes already well underway. Specifically: Sea-level rise.

"I would say three or four years ago there was—and this a general statement, not specific to New York—the emphasis was on mitigation; in other words, reducing our contribution to climate change," David Bragdon, head of the Office of Long-Term Planning and Sustainability, told Capital in an interview. "It's only more recently that policy makers are acknowledging what scientists have known, which is that even if we magically stop emissions tomorrow—if we were successful in all these mitigation efforts, there's still effects that are happening already."



Acknowledgement of the science meant that a great deal of the chapter on climate change in the 2011 revised PlaNYC is devoted to sea-level rise, partly coming from recommendations of the New York Panel on Climate Change, convened expressly for this sort of thing.

The panel believes that the sea level will rise as much as two to five inches in the 2020s, and reach the double digits as early as the 2050s.

"I think it's not understood how serious the situation will be in coastal areas and what the costs will be to society at large," said professor Klaus Jacob of Columbia's Earth Institute, a member of the panel. "This will go into any urban area that's on the coast into tens of billions of dollars."

It is, somewhat obviously, more exciting and uplifting to green the city and spare future generations the depredations of environmental change than it is to contemplate the inevitability of a serious flooding disaster in our lifetime.

But despite the great deal of research and information that has emerged in the last several years, Jacob said, "greening" projects are still proceeding largely without heed of potential disaster. Government bureaucracies, even those that operate in the generally forward-thinking Bloomberg administration, aren't always quick to act on new research that outlines new risks.

Another key initiative of the Bloomberg administration has been the transformation of the city's waterfronts. It's been a boom on the waterfront and the plans are only just beginning to be realized. None of them, Jacob said, take sea-level rise into account.

Further, the updated PlaNYC, called PlaNYC 2030, released last year, underlines a potentially competing problem: The city's population is expected to rise by 1 million people by 2030, and in order to accommodate all of them, a building boom is in order. Little in the guidelines or siting of new development in the plan seems to account for rising sea levels, either.

There has already been an enormous amount of capital investment in areas that are vulnerable to sea-level rise, and flooding. At the World Trade Center site, for example, the foundations are being built in what is actually called the "bathtub," as is the the very expensive new transit center there. Jacob names that as the area of the city with the most "risk." Jacob cites Columbia University's development plans in Manhattanville as particularly problematic, too.

Assessing this kind of technical "risk" is actually something of a formula. It is, according to Jacobs, not simply a matter of mapping out areas most likely to flood, but "a product of three things: the asset value; the hazards that it's exposed to; and the vulnerability of those assets with respect to the hazards."

Risk, then, from a scientific and economic point of view, is "the potential dollar-loss per unit-time," which "can be very large when the asset value is very large."

But let's say, in a worst-case scenario, that parts of the city or one or some of its systems flood completely in an event like what planners call a "100-year storm" (a storm so severe its likelihood is estimated at one percent in any given year).

Many of them will not rate under the economic definition of "risk," because the value is too low. And this is where the standard risk-assessment falls apart: It is scientific and political; it does not factor in entire low-lying neighborhoods with low-rise housing under water.

Then there are infrastructure systems, which, compromised in one place, can spread mayhem far and wide. Water supply, sewage treatment, and energy supply, all built largely underground, mostly many years ago, are potentially vulnerable.

Bragdon said the administration is really beginning in earnest this year to assess risks to those three key areas. Any institution that has assets that could be affected by climate change is in his purview, which means not only the city's own, but those of private providers, like Con-Ed, which be a part of the process.

Bragdon and Jacob agree that the Department of Environmental Protection, which has jurisdiction over the sewage treatment plants, is probably the farthest along in planning for climate change—Jacob said he believes they "have a relatively good program to deal with this," and "are probably the most capital-intensive agency and the most on the ball," and Bragdon said it is likely "the farthest along."

"Just this morning," Bragdon said,"we were having a conversation with someone about, like, if the sewer outfalls from these plants are basically based on gravity—that the water goes down into the bay or the river or whatever it is, as sea-level rises there's not much fall, or even it becomes a negative number.

"In that case, obviously, you wouldn't design it that way again if you were building a new one. You'd account for 50 or 60 years from now; it's going to be a different delta between current water level and where it is now. They're looking at things like pumps. Do pumps need to be raised? Or do pumps need to be installed somewhere? And I think that has factored into some design decisions that already are being made on new assets under construction, like at Bowery Bay [pdf], for example, out near Astoria."

Then, of course, there is the flooding that comes with extreme weather events.

PlaNYC's plan for Governor's Island specifically develops it to handle flooding, and absorb some of the storm surge that might come during an extreme weather event; the design calls for ripping out asphalt barriers, grading the waterfront promenades and finding trees that can survive when they have been covered by brackish water.

The same sort of thing is taking place in other parts of the city—"soft edges" is the term often used for the creation of more surge-resistant permeable surfaces, like wetlands, to buffer land from sea, instead of the impermeable surfaces like asphalt and concrete that presently make up much of the city's coastline.