I was pleased this afternoon to see that the questions I posted here last night about where Rikers Island  fit into New York City’s evacuation scheme for Hurricane Irene were being asked all over Twitter and the blogosphere. I knew something was up when I saw the metrics on that post take an immediate spike, in both visits and referrals from Google. Clearly a lot of people were not writing off the Rikers residents even if the mayor and the city’s disaster planners were not going out of their way to include them in the discussion.

It occurred to me that the city might consider a Rikers evacuation too sensitive to be dealt with publicly–which could very well be true given that the prisoners would be moved to someone’s backyard, and, of course,  “not in my backyard” syndrome is as endemic to New York as  to any other part of the country. This  would not rule out that the administration actually has been attending to the Rikers population out of the public eye. On the other hand, it doesn’t rule out their NOT attending to the Rikers population, either.

In any case, I noticed in one discussion on this controversy on Twitter that the elevation of Rikers Island relative to other parts of New York came into clearer focus. Eric Umansky of ProPublica helpfully provided a link to a Google Map adapted to show altitudes of specific locations. It’s  not a permalink, so you need to work it to find the elevations you’re looking for. I’ll spare you the trouble and report my own findings.

In a nutshell: Most of Rikers is in the range of 20 to 40 feet above sea level. Compare this to most of LaGuardia Airport’s runways (1 to 10 feet) or Long Island City (1 to 15 feet)  in the city’s evacuation Zone A, which was mandatorily evacuated yesterday. Roosevelt Island, which is in Zone B (at risk from Category 2 hurricanes) is in the range of 10 to 15 feet above sea level. Astoria, in Zone C  (at risk from Category 3 hurricanes) ranges 15 to 20 feet.  By comparison, most of the Upper West Side is 50 or more feet above sea level and in no danger of flooding.

Thus, it would seem that Rikers is, like my neighborhood of the Upper West Side, in no need of being evacuated. To bring that point home to myself, I Googled “NYC global warming map” to see if I could replicate the surge levels the city is anticipating from a worst case scenario visit from Irene.  I found this at Geology.com:

The map clearly shows that a sea level rise of only a few meters would inundate thousands of acres of highly developed land on Long Island, Manhattan and the New Jersey coastline. In New Jersey large areas around Newark Bay and Arthur Kill will be flooded. And some of the greatest land loss to New York will be the Atlantic coast of Long Island. There the sea will flood deep into the flatly sloping coast of Long Island. Airports, ports, railroads, housing developments, highways, factories and industry would suffer billions of dollars in losses. New York and New Jersey have a lot at risk to sea level rise associated with global climate.

But if you do the simulation, you’ll see that it would take a rise of more than 6 meters (about 36 feet) (about 19 feet [thanks to Aaron Levitt for the correction]) before Rikers would begin to “sink” into the sea. Does this make me feel better about the elision of Rikers from the evacuation plan? A little better, yes. I’m still troubled by the fact that we are talking about an island accessible only by boat and a single bridge. Could something happen to the bridge in a Category 3 storm surge? And what about Category 4 or 5 storms?

These are questions that should not be put to rest when Irene begins to sink into the sea of memory.