Special research scientist
Lamont-Doherty Earth Observatory, Columbia University
Barriers are not sustainable structures for more than 100 years, so they will not be sufficient for, say, 500 years of sea-level rise. Barriers can work, but you should only build them if you have [a plan to update them]. Hurricane Katrina in New Orleans overcame man-made barriers because the city kept [sinking] and the sea had risen after the levies and walls went up. You have to take action behind the barriers to prepare for their obsolescence—before you design and build them.
They need to do both. Even better, focus on land use and municipal planning. Most immediately, buildings on low ground should pull all their systems out of basements and put them on higher floors. Tall buildings should put their systems on the 10th floor—let the lower level be a parking garage or something. Then waterproof the basement and low floors. In New York City, transportation systems such as subways have to close all ventilation grates at the street level and find other ways to vent. Gates are needed for subway entrances, or the entrances should be redesigned. In Taipei, for example, at some stations you have to walk up from street level to enter before you can walk down below street level into the subway.
Yes, we should retreat in certain low-lying areas. Insurance companies will not insure any property that is at a dangerous elevation. National flood insurance should also be revised; it is almost a hoax right now.
Every location needs a customized plan. But we also need to change land use up and down the U.S. East Coast. We must overcome “municipal home rule” by towns so that states or regions can implement sensible land-use policies. That will be a huge political battle, but home rule can make larger solutions almost impossible.