Sea Level Rise Will Flood Hundreds of Cities in the Near Future

Many shore communities in the U.S. face inundation in the coming decades.

Sea level rise caused by global warming is usually cast as a doomsday scenario that will play out so far into the future, it’s easy to ignore.  Just ask anyone in South Florida, where new construction proceeds apace.  Yet already, more than 90 coastal communities in the United States are battling chronic flooding, meaning the kind of flooding that’s so unmanageable it prompts people to move away.

That number is expected to roughly double to more than 170 communities in less than 20 years.

Those new statistics, compiled in the first comprehensive mapping of the entire coastline of the Lower 48 states, paint a troubling picture, especially for the East and Gulf coasts, which are home to some of the nation’s most populated areas.

By the end of the century, chronic flooding will be occurring from Maine to Texas and along parts of the West Coast.  It will affect as many as 670 coastal communities, including Cambridge, Massachusetts; Oakland, California; Miami and St. Petersburg, Florida; and four of the five boroughs of New York City.  The magnitude of the coming calamity is so great, the ripple effects will reach far into the interior.

The Union of Concerned Scientists, in a new report published Thursday in the peer-reviewed journal Elementa, mapped the rate of sea-level rise for the first time for hundreds of coastal communities—in an online feature that allows viewers to zoom in from a bird’s eye view all the way down to street level. The report also creates a timeline when sea-level rise is projected to inundate various percentages of coastal communities—and then delves into the politically and economically sensitive arena of what to do about it.

Options are limited. All are costly, whether adapting to a watery future with seawalls and other barriers, or retreating and finding a new place to call home.

When Does Flooding Become Intolerable?
“We knew we were going to be going out ahead of where anyone has gone before, but this is where the science took us,” says Erika Spanger-Siegfried, the report’s co-lead author.  “We recognized we were going to have to offer something useful to communities in the way of solutions.  We wanted people to see this coming, to give them a sense of the time they have before this becomes untenable, and outline things they can do to respond.”

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