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Over 14,000 Miles of America’s Coastline is Covered in Concrete

14 percent of America’s coastline is coated in concrete — and that could actually be really bad

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smithsonian.com

If you live near the beach or just go for an occasional swim, you’re probably familiar with the bulky concrete walls that protect buildings, homes and streets from the ocean’s crashing waves. Scientists call those fortifications “hardened shoreline” — and it turns out that humans’ efforts to shield themselves from the ocean could backfire.

Science’s Gabriel Popkin reports that nearly 14 percent of the coastline of the United States is “coated in concrete,” and that number is expected to rise to a third by the year 2100. These “armored” areas are especially common in Boston, San Francisco and much of Florida, writes Popkin.

A team of marine researchers recently used data from the National Atmospheric and Oceanic Administration (NOAA) to figure out just how much coastline is covered in concrete, then factored in variables like population density and the prevalence of storms to assess how shorelines impact the ocean. What they found was that 22,842 km (a little over 14,000 miles) is fortified with concrete. What's the problem with that? Well, concrete walls can bounce waves back into the ocean, destroy tidal marshes and hurt wildlife, and even make coastal areas more vulnerable to storms.

There’s a better way, argues the team: Opt for living shorelines using structures like marsh shills that provide and preserve natural habitats instead of pouring on the concrete. The researchers note that the effectiveness of these living barriers have not yet been tested, but they think they’re a better option than seawalls and bulkheads that foster beach erosion.

“In one [North Carolina] region, 76% of bulkheads surveyed were damaged, while no damage to shorelines with sills was observed,” notes the team. The idea of living sea barriers instead of concrete may set survivors of hurricanes like Irene and Sandy on edge, but in fact it’s already being adopted by states. “[Concrete beaches] may have been acceptable in the past, when seawalls and bulkheads replaced many of our beaches” notes the state of New Jersey in its manual for coastal hazard mitigation, “but our beaches are being brought back by artificial nourishment projects.”

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