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I react a certain degree of skepticism when I see that a piece of built environment in New York is labelled as “interim.” There are many reasons for this, with the best example being that the Guastavino dome over the crossing at the Cathedral of St. John the Divine, constructed in 1909 as a temporary roof, is not only still the roof, it’s now a designated landmark. In any case, that’s a picture up above of one of the flood barriers that is part of the city’s Interim Flood Protection Measures Program. Here’s a close up on the placard:

This barrier is along the East River waterfront downtown:

To answer a few of the most obvious questions: yes, that’s the Brooklyn Bridge in the upper right, a bit north of where I was standing; yes, a portion of the elevated highway is painted purple for no obvious reason; and yes, the barrier is set up inboard of the pedestrian walkway and bike path. This is an emergency barrier, intended to prevent a repeat of the flooding downtown Hurricane Sandy during a similar isolated event. In the long run, there are plans for raising the bulkheads and creating other barriers to deal with some measure of sea-level change.

Obviously, the success of this kind of effort depends on how severe you expect future events to be. It’s not clear how to plan for the worst case scenarios in New York or in any other sea-facing city. So people plan for scenarios that can be addressed. I’ve also discovered that people generally misunderstand the threat here. Most of the city is more than 10 meters above sea level, and if we have enough global sea rise that would make that a problem, the issue is not protecting New York, it’s protecting everything. There are portions of the city that are quite vulnerable because they are low-lying: for example, Alphabet City in Manhattan, the south shore of Staten Island, the Rockaway peninsula in Queens, and the shores of Jamaica Bay in Brooklyn and Queens. However most of the city is well out of the danger zone for the next fifty years, even assuming severe sea-level rise. New York is neither flat nor sitting on bad bedrock.

The danger, as we found out during Sandy, is that a lot of our infrastructure is not designed for flooding. A good amount of damage was done to the East River subway tunnels that flooded as the stations in low-lying areas flooded, and we’re just now, a decade later, finishing up those repairs. There’s been a program, far less visible than those canvas-and-wire cubes of sand in the photos, to replace the subway ventilators in low-lying areas with ones that can be rapidly closed off if a hurricane is approaching. Similarly, creating temporary storm barriers for the tunnels is readily doable. These, too, fall under the heading of interim measures, but they can buy a good amount of time until (a) we can address carbon emissions and (b) better protective measures can be built.