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How Sea-Level Rise Could Overwhelm Your City

As the floodwaters rise, some people are going to be getting a bit wet. But where will be safe? A new map shows you where the new shoreline will be.

As recent disasters in Louisiana, Japan, and Thailand have shown us, few things are more terrifying than when water engulfs what used to be dry, habitable land. Climate change and its accompanying sea-level rise will force anyone living in a coastal area to confront the realities of flooding. According to a new study from Climate Central, that’s a pretty large group, with 3.7 million people in the U.S. living within three feet of the high-tide line—areas likely to be overwhelmed by sea-level rise. Five million people live less than four feet above the high-tide line.

Who will be hit hardest by rising tides? Climate Central put together an interactive map, dubbed Surging Seas, to let users see what will happen to the land if water levels rise anywhere between one and 10 feet. Note: many—but not all—researchers expect the sea level to rise three feet by 2100.

The researchers used 55 tidal gauges across the U.S. to show how sea-level rise will influence the water levels from projected storm surges, as well as how often high water levels will occur as a result.

In the New York City area, the researchers’ model projects that water will inundate the coast. Statistics accompanying the map explain that over 64,000 people live within 1 foot of the tide line. There is over a one in six chance that sea levels in combination with a storm surge and high tide will overtop 1 foot by 2020 at the New York Harbor (the nearest flood risk indicator site).

In New Orleans, the only city with more people living in the 1-foot zone than NYC, over 249,000 people are at risk of being inundated by water in the event of climate change-triggered flooding. As in NYC, the chances of that happening are greater than one in six by 2020. The big difference: We’ve already seen the damage that could occur in this city. And just the smallest increase in sea level can greatly increase the odds of a "hundred year flood."

Other at-risk areas include parts of Florida, Virginia, New Jersey, Maryland, and North Carolina.

Even people who think they’re protected by topography or human ingenuity might not be. The Climate Central researchers explain that certain locations appear "isolated on the surface but might experience impacts via reduced drainage, via channels too fine to appear in [digital elevation models], or via porous bedrock." In past studies, researchers have only looked at the threat in relation to elevation above sea level. Instead, Climate Central looked at proximity to high tide—potentially a more accurate indicator of who will get hit the hardest.

One day in the not-too-distant-future, coastal city governments may beg their inland neighbors to spew fewer greenhouse gases, lest the coasts get continually battered by flooding. Consider the situation in the Maldives, a series of islands in the Indian Ocean that are at immediate risk from sea-level rise, to be a warning.