Climate Change, Sea Level Rise Spurring Beach Erosion
School’s not out yet for all kids, and summer doesn’t technically start for another month, but for anyone living within striking distance of the ocean — especially in places that experience cold winters — this Memorial Day holiday weekend marks the traditional start of beach season. It’s time to check whether last year’s sunscreen is past its expiration date, dig the bathing suit out of the bottom drawer, and wonder why you didn’t get back to the gym months ago to get into some semblance of shape before venturing out onto the sand.
Most beachgoers don’t stop to wonder, though, whether the sand will be there when they arrive. But beaches are a lot more transient than they appear. The constant pounding of waves, especially during storms, plus the scouring action of currents, constantly washes sand away from some stretches of coastline and deposits it somewhere else. Some beaches naturally tend to shrink, while others grow.
Over time, things tend to even out, but in recent years, for many parts of the U.S., the trend has been toward shrinkage: a recent study by the U.S. Geological Survey, for example, found that 68 percent of the beaches in New England and the Mid-Atlantic states are eroding; USGS studies further south along the Atlantic and around the Gulf of Mexico are still ongoing, but according to Asbury Sallenger, who is overseeing those studies, “some barrier beaches in Louisiana are eroding by 20-plus meters [65 feet] per year. Not all of them, but enough to get your attention.”
While beach erosion is perfectly natural, human activity has made it worse. When sand dunes are bulldozed to make way for condos, for example, or when the grasses that keep them intact are trampled by sun worshipers, waves that would normally break harmlessly can wash further inland, sweeping away sand at a greater rate. Sea walls can protect inland areas, but their rigid structure accentuates the waves’ scouring behavior, which can up the rate of beach erosion.
Groins (pier-like structures made of rock that extend from the beach out into the water) can keep sand from drifting down the coast, but at the expense of the beaches downcurrent. And the more massive constructions known as jetties, built to keep sand from clogging harbors, can starve beaches even more severely. Folly Beach, in South Carolina, has lost enormous amounts of sand thanks to two long jetties constructed in nearby Charleston more than 100 years ago.
And then there’s the growing danger of sea level rise, caused by climate change. “Even 25 years ago, sea level was rising,” Sallenger said in a recent interview, “but not a heck of a lot.” But that’s changing as the planet’s temperature keeps going up, sea water keeps expanding and ice is flowing faster to the ocean, especially in Greenland and Antarctica. “If sea level rises another foot,” said Duke University beach expert Orrin Pilkey in an interview, “the shoreline in northeastern North Carolina could be pushed back 5 or 6 miles. And all of the projections I’ve seen suggest it will be more like 3 feet by 2100.”
Even without this added factor, beach erosion has proven to be a big problem for those who own oceanfront property or work in industries related to beach tourism. In response, cities and towns up and down the coast have resorted for years to what’s known as beach nourishment or beach replenishment — bringing in new sand to replace the sand that’s disappeared.
During the first week of June, for example, the village of Key Biscayne, Fla., will start trucking in 44,000 tons of sand to build its beaches, at a cost of $1.67 million. In March, Atlantic City, N.J., beefed up 5.1 miles’ worth of beach in an $18 million operation. In Port Saint Joe, Fla., a beach-replenishment project was completed in 2009 at a cost of $22 million, but a quarter of the sand is already gone. Officials have petitioned the federal government for another $15 million to repair the damage. A study published more than a decade ago pegged the annual cost of beach replenishment at $100 million — but it didn’t include the West Coast, and costs have gone up since then.
That figure, plus the untold millions more poured into sea walls and other beach-preservation measures, would be drastically lower if people didn’t love the seashore so much. “It’s beautiful,” Sallenger said. “Everybody wants to live there. So you build a structure, and it turns into a whole line of condos.” Then, he said, a storm or two comes along, the beach is partially washed away, and the condo owners demand action. “Once you build a fixed structure,” Sallenger said, “you have problems.”
Those problems have gotten dramatically larger over time. If you look at hurricane-prone stretches of coastline alone, about 14 million Americans lived in harm’s way in 1960; by 2009, the number had tripled. “In a lot of places,” Sallenger said, “it’s becoming difficult to find enough nearby, high quality sand to meet the demand.”
As the ocean rises, beach replenishment will get even harder. “With even a 2-foot rise,” Pilkey said, “there will be just too great a rate of loss. Then the question becomes, ‘should I buy a house on the shore? Should I build one? Will my children inherit it?’ Probably not, in my view.”
For now, however, the prospect of rising seas, along with the climate-change-related expectation that Atlantic hurricanes could become more powerful in coming decades, hasn’t had any discernible effect on coastal development. “It’s kind of frightening,” Pilkey said, “to think of the possibilities.”
So if you’re heading for the beach this weekend, or any time this summer, it might be a good idea to take a good, hard look at the expanse of sand that surrounds you. It could be something you’ll want tell your grandchildren about.