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

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Flooding at the 23rd-Ely subway station. ()
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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."

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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.

Hard edges mean that when there is flooding, water rushes over the roads and can't move backward; permeable surfaces catch much of the surge in the vegetation, or at least slow the water down, and give it a natural retreat.

The city's new Zone Green initiative encourages "green roofs," where rain coming down would be partly absorbed by the vegetation instead of spilling into the street.

AND ALL OF THIS BEFORE YOU RECKON WITH ONE OF THE MOST serious concerns: In the event of one of these major storms, transportation networks are exceedingly vulnerable.

This consideration was in the background of the much-misunderstood shutdown of the entire transit system as the city awaited hurricane-turned-tropical-storm Irene. The shutdown allowed the M.T.A. to pull trains out of areas that might flood and otherwise prevent damage from the storm, instead of trying to operate during it, or fix it afterward.

The scenario for transportation in a 100-year storm might seem remote, until you consider the subway has not yet had to weather one; the subway system was opened in 1904, and many of its most vulnerable sections were built in the years immediately following.

Imagine a scenario in which a 100-year-storm flooded all of the parts of the system that are most susceptible—the tunnels that carry trains under the East River to and from Manhattan, and the major connection points in Lower Manhattan. Then Brooklyn, Queens and Long Island would essentially be cut off from the mainland for the millions of commuters who pass through those links every day. And not for a short time.

"Essentially the subway system will be shut down and the restoring time will be at least a month," Jacob said. "And probably many months."

In the same way that many people, during Irene, didn't understand why it took so long to shut the system down and so long to start it back up, if there is that kind of flooding, they will have to pump all the water out of the tunnels, take out the signal systems, wash them off (because they will have been in touch with brackish water), dry them, put them back together, test them, and reinstall them. And since much of the subway system is as old as 100 years, new parts cannot exactly be ordered up immediately; new ones would probably require starting from scratch.

The M.T.A. has prepared a report for the Federal Transportation Administration, called "State of Good Repair in the Era of Climate Change." A case study in the same document reports that the M.T.A. has partnered with Columbia University, and that "it had the first publicly available report on the impact of climate change on a transportation system in the country."

But it is also an agency that does not get its money from New York City; it's the state legislature that decides how much public money will go to the authority. This, historically, has been a problem for transportation networks that don't stretch beyond the limits of the city, and it still is. For massive capital projects, the political will could be hard to assemble for significant projects.

And in the meantime, the M.T.A. has been in financial trouble, funding much of its ongoing operation and "state-of-good-repair" work with bond issues, which is not feasible in the long term and doesn't leave much room for large capital projects that would normally depend on such financing.

So far the M.T.A. has been taking smaller, less expensive measures to prepare for flooding and sea-level rise. They are raising sidewalk grates that vent stations and tunnels and putting bicycle racks on top of them, and building concrete platforms a few inches high in front of the entrances to stations.

Before Bragdon took his current position, the New York City Green Codes Task Force had begun to assess what sea-level rise projections might mean for the areas most likely to flood, so, Bragdon said, "we can base out investment in infrastructure on remapping flood zones, all that can be based on the best projections. That was the first step."

The next step in that process, which the administration is starting to do, is to come up with a "risk index" that Bragdon said "endeavors—within the realm of a certain amount of uncertainty—to do some projective cost-benefit analysis in terms of where the risks are, relative to things like land value or population density."

Historically, it has been the Federal Emergency Management Agency that defines flood zones. But these maps have serious shortcomings: they are based on only the 100-year-storm scenario; they were developed for a flood-insurance program that had nothing to do with planning; and most importantly, they are based on past records, and are decades out of date on the scientific projections for sea-level rise.

"The flood insurance maps haven't been redone here since, like, some point in the 1980s," Bragdon said, "and so we're going to be partnering with [FEMA] to update those," beginning "in earnest" this year.

Further, through a federal grant program, the city will actually have someone from FEMA in the office; new draft maps will probably come out early in 2013.

This batch of new maps will be developed using new data collected partly from fly-over maps, Bragdon said.

"We're going to be using that to also look forward, and incorporate anticipated sea level in the future, which seems like it's a common sense thing, but apparently hasn't been done," he said.

ANOTHER PART OF PLANYC DEALS WITH the fact that there will be population growth.

According to PlaNYC calculations, the city's population will increase by one million before the year 2030. That means that the city must build.

And sea-level rise means that housing is an issue both in the sense that the city does not have enough of it, and in the sense that some of it might end up underwater.

It's new building where Jacob thinks that, with regard to sea-level rise, city (and other cities) is most likely to go wrong.

"You have to stop building more assets in a risky way in flood zones," Jacob said. "Start with avoiding bad things for the future."

When development is being considered, "follow the flow of the money—that's the key. Wherever money is being spent, that's where you have to watch out."

Planned developments are supposed to factor in sea-level rise. For the most part, they haven't.

"[Sea-level rise] has to be integrated like many other elements, like environmental impact statements and so on—it just has to be part of it," Jacob said. "You have to ask yourself, when you do a project, is that a project that has a lifetime of 100 years? Or is it likely to be still around in 200 or 300 years? And the city doesn't go away, but it will change, and so you have to take into account roughly the time horizons for which you want to build something without having to change it in the middle of its lifetime."

Bragdon has also considered new building regulation, of course.

"That's another one of our initiatives in terms of whether we may strengthen some of the regulations that are applicable to areas that may be flood zones in the future," he said. "And how, whether a building needs to be elevated, or that the first floor needs to be elevated in some way. So that's a possibility."

Ironically, perhaps, the waterfront is considered one of the most viable--and valuable--places by many developers to concentrate new high-density housing.

Recently, the nascent Center for Urban Real Estate at Columbia University's, released a plan for a whole new neighborhood: LoLo (as in Lower Lower Manhattan). To make LoLo, the city would connect Governors Island to Lower Manhattan with infill that would connect it to Lower Manhattan, essentially extending the island. Developers could then start building on that land.

Though PlaNYC, as mentioned, specifically expects and is preparing for Governors Island to flood. But Vishaan Chakrabarti, a professor of real-estate development at Columbia's Graduate School of Architecture, Planning and Preservation, and the head of the new group, said that the designers of LoLo did plan for sea-level rise, and that LoLo would be built with the expectation of it.

"Unlike Lower Manhattan today, it would actually be designed to take a certain amount of flooding in the future," Chakrabarti said over the phone, "Like there would be elevated walkways to evacuate people, and subway stations would be designed differently, and the buildings would have a different relationship with the ground plane, all to deal with flooding situations. There would be soft edges and a ring of barrier islands to protect it from storm surge."

"I think it's consistent with PlaNYC in two ways. One, is that it does try to proactively deal with the storm surge, sea-level rise in a very, very, activist way. But the other way in which it is consistent with PlaNYC is that PlaNYC calls for a million new New Yorkers by 2030, though it's not very clear where those millions New Yorkers are going to live and work and play."

Jacob is opposed to building more low-lying land, and suggested we increase density on higher land we already have, making a retreat from the shoreline.

Bragdon's thoughts were similar.

"Obviously the city's going to have to accommodate more people than it currently does, but I don't think filling in the harbor is probably the most cost-effective way to do that," he said.

More housing will likely be created through selective rezoning of various areas that have seen investment and that are near transit centers, like Downtown Brooklyn.

But the biggest problem by far has to do with an area much of which was built up to near-maximum density deeds ago: Lower Manhattan.

Its risk index is extraordinary: It's low-lying, and the amount of capital investment, both new (since the destruction of the World Trade Center) and longstanding (it is after all the center of the world financial system) is extremely high. There may have to be levees, flood walls and pumping systems put in place. In individual skyscrapers, any low-level floor that has any value would be moved up to, say, the 10th floor, in any plan that seriously accounted for sea-level rise.

Lower Manhattan presents the difficulties of retrofitting to protect against sea-level rise in at-risk, densely developed areas.

You would have to arrange "below ground, or floodable ground, either in such a way that you would put hermetic gates that really seal them tightly," Jacob said, "or you would transform them into garages, and before the hurricane arrives, you tell everybody, ‘bring your cars to higher ground, good luck.' Or leave it there and try to get the insurance to pay for it.'"

Big ideas involving huge capital investment are constantly being developed to deal with sea-level rise, but few are practical.

One of those types of things that comes up frequently is sea-walls, which are exactly what they sound like: giant walls planted in the ocean that keep water from hitting the shore.

Both Bragdon and Jacob are highly skeptical of anything of that nature.

"In terms of these large highly engineered structural solutions, that's certainly not the first place we're going to look," Bragdon said, although he added that they probably will study it with the Army Corps of Engineers (and also that it would take an act of Congress to get it done), "we'll have to do it with a very rigorous cost-benefit context in mind."

New York is situated on an estuary, Bragdon said; it doesn't have one seafront. So even the placement of those kinds of walls would be a bet on which waterfront will be hit the hardest in a particular event.

One plan Jacob has said he is "quite strongly against" would build seawalls near the Verazzano-Narrows Bridge, near the Whitestone Bridge, and somewhere in the waterways that separate Staten Island from New Jersey, which, if seawalls were built, would be the most obvious places to put them.

But that would leave all of southern Brooklyn, and other areas, exposed, and Bragdon also considered that a great deal of flooding from Irene came down, not from the ocean but from rainfall upstate.

"Sooner or later we would be in a situation like New Orleans," Jacob said, invoking the dreaded example of Hurricane Katrina. He talked specifically about the possibility that seawalls and levees that are built become expensive to maintain, meaning a constant battle for maintenance resources; and, regardless, it's likely that as soon as seawalls were built, they would have to be built higher. Failure for that kind of investment would be an enormous waste.

New York City, and the United States in general, are just beginning to deal with sea-level rise and its consequences. But there are places that have always had to think about keeping the water away for centuries, for example, the Netherlands, where about a quarter of the country is actually below sea-level, and half is just barely above.

The Netherlands has a system that protects it from a 10,000-year storm, Jacob said.

Or, they did. After factoring in sea-level rise, Jacob said, "they realized that over the next half-century to century that it's not anymore one in 10,000. It's, at best, one in 100."

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