Monday, November 26, 2012

Projected Sea level rises in various American cities

We recently reviewed a wonderful web site at the New York Times that allows you to visualize in maps how much flooding would take place in various American cities under different time frames (in years) and scenarios of extent of rise based on historical records (from long, LONG ago) as well as current scientific calculations based on rising temperatures.

This is what the slider looks like that gives you scenario choices:

The maps are very visually compelling because they show under water land in light blue so you can actually imagine what the flooding would do to, say Charleston, South Carolina which under the worst scenario (25 ft rise) would be 80% flooded or Galveston, Texas which wouyld essentially be history - 100% under water.

The follwing is a partial screen shot of what these maps look like:

In the first partial frame you can see that Miami Beach is gone. Remember it's a barrier island so that's not surprising. But more daunting is that 39% of New York City would be flooded, something that seemed ridiculous a few years ago but is now not so far fetched after "Superstorm" Sandy.

Here are some flooding percentages based on the 100-300 year five foot projection:
  • Miami is 20% flooded; Miami Beach 94% under water
  • In Boston the city of Cambridge is 26% flooded
  • While only 5% of Long Island, New York floods, "Barrier islands start to submerge; other islands in Middle and East Bays disappear. Shore of main island moves inland." You think Hurricane Sandy was devastating! You should look at the map of LI.
  • Not surprisingly New Orleans 88% is flooded and that's a city that has been armored with levies dykes, and a massive pumping system. 
  • In Tampa, Florida "Tampa Bay pushes inland one to four miles and eats away at MacDill Air Force Base. Beach communities flood."
For policymakers and students of Coastal Zone Management these numbers are at the very least interesting. We would add that they are actually critically important because ignoring data and science does not make bad things go away (just ask smokers who ignore the warnings.)

The real difficulty is that for politicians it is almost impossible to take significant action which would displace and move people and human structures from the threatened areas. The problem is that first of all no one believes any of this applies to THEM and second, it's a hundred years or a hundred THOUSAND years from now so "who cares!"

We have interviewed dozens of local government officials all of whom have expressed doubt that proactive action is realistic. People and local governments are simply too welded to their property and their beach/coastal location which they, of course deeply love.

If you want to play with this app you can go to

The maps are based on the following assumptions: "Notes: These maps are based on elevation data from the U.S. Geological Survey and tidal level data from the National Oceanic and Atmospheric Administration. Maps show the extent of potential flooding relative to local high tide.

The 25-foot sea level rise is based on a 2012 study in the journal Science, which augmented findings from a 2009 Nature study. They found that 125,000 years ago — a period that may have been warmer than today but cooler than what scientists expect later this century without sharp pollution cuts — the seas were about 20 to 30 feet higher than today. If temperatures climb as expected in this century, scientists believe it would take centuries for seas to rise 20 to 30 feet as a result, because ice sheet decay responds slowly to warming."

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