How to protect New York from disaster

By Felix Salmon
September 11, 2012
Mireya Navarro's article about the risk of natural disaster -- flooding -- in New York.

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Today, September 11, is a day that all New Yorkers become hyper-aware of tail risk — of some monstrous and tragic disaster appearing out of nowhere to devastate our city. And so it’s interesting that the NYT has decided to splash across its front page today Mireya Navarro’s article about the risk of natural disaster — flooding — in New York.

Beyond the article’s publication date, Navarro doesn’t belabor the point. But in terms of the amount of death and destruction caused, a nasty storm hitting New York City could actually be significantly worse than 9/11. Ask anybody in the insurance industry: a hurricane hitting New York straight-on is the kind of thing which reinsurance nightmares are made of. And as sea levels rise in coming decades, the risks will become much worse: remember, it’s flooding from storm surges which causes the real devastation, rather than simply things blowing over in high winds.

So, what can or should be done? One option is to basically attempt to wall New York City off from the Atlantic Ocean:

A 2004 study by Mr. Hill and the Storm Surge Research Group at Stony Brook recommended installing movable barriers at the upper end of the East River, near the Throgs Neck Bridge; under the Verrazano-Narrows Bridge; and at the mouth of the Arthur Kill, between Staten Island and New Jersey. During hurricanes and northeasters, closing the barriers would block a huge tide from flooding Manhattan and parts of the Bronx, Brooklyn, Queens, Staten Island and New Jersey, they said.

Needless to say, this solution is insanely expensive: the stated price tag right now is $10 billion — well over $1,000 per New Yorker — and I’m sure that if such a project ever happened, the final cost would be much higher. And such barriers don’t last particularly long, either. London built the Thames Barrier in 1984, and there’s already talk about when and how it should be replaced. And building a single barrier across the Thames is conceptually and practically a great deal simpler than trying to hold back the many different ways in which the island of Manhattan is exposed to the water.

What’s more, there’s an environmental cost associated with barriers, as well as a financial cost. Which cuts against the kind of things which New York has been doing. They’re smaller, and much less robust. But they improve the environment, rather than making it worse. And they’re relatively cheap. For instance: installing more green roofs to absorb rainwater. Expanding wetlands, which can dampen a surging tide, even in highly-urban places like Brooklyn Bridge Park. Even “sidewalk bioswales”. (I’m a little bit unclear myself on exactly what those are, but they sound very green.)

Adam Freed, the outgoing deputy director of New York’s Office of Long-Term Planning and Sustainability, talks about making “a million small changes”, while always bearing in mind that “you can’t make a climate-proof city”. That’s a timely idea: we can’t make New York risk-free, and it’s not clear that it would make sense to do so even if we could. After all, as we all learned 11 years ago today, it’s impossible to protect against each and every source of possible devastation.

Other cities have similar ideas:

In Chicago, new bike lanes and parking spaces are made of permeable pavement that allows rainwater to filter through it. Charlotte, N.C., and Cedar Falls, Iowa, are restricting development in flood plains. Maryland is pressing shoreline property owners to plant marshland instead of building retaining walls.

Still, all of this green development does feel decidedly insufficient in comparison to the enormous risks that New York is facing. I like the idea of a “resilience strategy”, but there are still a lot of binary outcomes here, especially when it comes to tunnels. Either tunnels flood or they don’t — and if they do, the consequences can be really, really nasty. Imagine a big flood which took out all of the subway and road tunnels into Manhattan, or even just the subway tunnels across New York Bay as well as the Holland Tunnel. As such a flood becomes more likely, the cost of protecting against it with some big engineering work — insofar as such a thing is possible — becomes increasingly justifiable.

And this is just depressing:

Consolidated Edison, the utility that supplies electricity to most of the city, estimates that adaptations like installing submersible switches and moving high-voltage transformers above ground level would cost at least $250 million. Lacking the means, it is making gradual adjustments, with about $24 million spent in flood zones since 2007.

Lacking the means? What is that supposed to mean? New York City has a credit rating of Aa1 from Moody’s; ConEd has a crediting rating of A3. Interest rates are at all-time lows. There has never been a better time to invest a modest $250 million in helping to ensure that New York can continue to have power in the event of a storm. Doing lots of small things is all well and good, and I’m not convinced that the huge things are necessarily worthwhile — or even, in the case of moving people to higher ground, even possible. But the medium-sized things? Those should be a no-brainer right now.

4 comments

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>>I’m a little bit unclear myself on exactly what those are, but they sound very green.

Ah, you’re being very tongue-in-cheek here, right? If not, my respect for you just went down several notches.

Posted by Curmudgeon | Report as abusive

Felix, with a rising ocean level, it won’t matter if you added a trillion square feet of green roofs and bioswales (by the way, for an example of sidewalk bioswales, see: http://goo.gl/ks7cL).

Green roofs and bioswales mitigate the need to expand sewer capacity and storm overflow, first and foremost. Because they divert storm water into natural filtration and slow the process of rain water flow, they buffer a lot of storm-induced river flooding.

But in a hurricane or as a result of global warming, a rising ocean with salt water would end up killing most of the plants in these bioswales. And the sheer amount of water would simply overwhelm the bioswales. You saw what happened when the tsunami hit Japan; it’s almost the same thing — a higher, localized ocean level (whether from a storm surge or a tsunami) cannot be mitigated, even if you had a million acres of farmland. The tsunami sea wall was their best hope, but it was too short.

If NYC is like most other cities in the US, then combined sewer overflow goes directly into a major body of water. Bioswales and green roofs help stop storm water from entering and overloading the sewer system which in turn prevents untreated sewage from being dumped. But what happens when the water table is so high (from either a storm surge or global warming), as to push that sewer water backwards? You’ve seen it occasionally but you might expect to see it with greater frequency in the future: crap flows backwards and up into homes.

A sea wall is only just the beginning.

Posted by GRRR | Report as abusive

Felix, with a rising ocean level, it won’t matter if you added a trillion square feet of green roofs and bioswales (by the way, for an example of sidewalk bioswales, see: http://goo.gl/ks7cL).

Green roofs and bioswales mitigate the need to expand sewer capacity and storm overflow, first and foremost. Because they divert storm water into natural filtration and slow the process of rain water flow, they buffer a lot of storm-induced river flooding.

But in a hurricane or as a result of global warming, a rising ocean with salt water would end up killing most of the plants in these bioswales. And the sheer amount of water would simply overwhelm the bioswales. You saw what happened when the tsunami hit Japan; it’s almost the same thing — a higher, localized ocean level (whether from a storm surge or a tsunami) cannot be mitigated, even if you had a million acres of farmland. The tsunami sea wall was their best hope, but it was too short.

If NYC is like most other cities in the US, then combined sewer overflow goes directly into a major body of water. Bioswales and green roofs help stop storm water from entering and overloading the sewer system which in turn prevents untreated sewage from being dumped. But what happens when the water table is so high (from either a storm surge or global warming), as to push that sewer water backwards? You’ve seen it occasionally but you might expect to see it with greater frequency in the future: crap flows backwards and up into homes.

A sea wall is only just the beginning.

Posted by GRRR | Report as abusive

When Irene came shooting up the Harbor, just such a scenario was possible.
Had the storm slowed down or altered course in such a way to intensify/prolong the surge, far more damage would have occurred. “Missed it by THAT much.”
That was the shot across the bow. No one seems to have taken notice.
Haven taken 6 inches of flooding in my apartment due to underground storm surge (that’s water surging through the ground from the nearby harbor), I am not likely to forget any time soon. At least we didn’t get sewage or 3-foot-deep flooding like some of our neighbors did.
If you really want to scare the hell out of yourself, look into earthquake scenarios. Thousands of unreinforced masonry buildings throughout the city. Brooklyn sitting on a “glacial moraine”, essentially a loose jangly pile of rocks left over from the last ice age. It only takes a shaker of about 5 to 6 on the Richter scale to trigger the worst disaster this country has ever seen: liquefaction, collapsed buildings, extreme catastrophe.
Luckily the frequency of such an event around here is every 300-600 years.
It could happen tomorrow or not for a few hundred years. No one knows, we won’t see it coming, and there’s no way to properly prepare for it.
Do you feel lucky?

Posted by bryanX | Report as abusive