Beaches Going, Going, Gone?

Science World, May 10, 1999 by Chana Stiefel, Michael Cannell

AMERICA'S BEACHES ARE VANISHING. SHOULD WE FIGHT TO SAVE THEM, OR LET NATURE TAKE ITS COURSE?

You're set for summer--shades, flip-flops, new swimsuit, maybe even a surfboard. There's only one problem: Where's the beach? Across the U.S., from Ocean City, New Jersey, to Oceanside, Oregon, sandy beaches are simply washing out to sea.

By some estimates, 80 percent of the U.S. shoreline is eroding, or wearing away, as hurricanes, winter storms, rising ocean levels, and building development pound away at the coast. In California alone, about 0.3 meters (1 foot) of dozens of beaches erode every year. Many of North Carolina's beaches are losing up to 1.2 m (4 ft) a year. Need more evidence?

* In March, engineers uprooted the Cape Hatteras Lighthouse, a 129-year-old historic landmark on the eroding Outer Banks of North Carolina. To keep it from being swallowed by the sea, they relocated the lighthouse 480 m (1,600 ft) from the current shoreline. When built in 1870, the lighthouse stood nearly half-a-mile inland from the coast. But after decades of coastal erosion, waves crashed just 37 m (120 ft) from the beacon.

* On the sun lovers' New Jersey shore, 53 kilometers (33 miles) of beach have disappeared in the last 10 years. Now, the U.S. Army Corps of Engineers plans to rebuild the beach at an estimated cost of more than $1 billion.

* In Oregon, rising seas and pounding waves, intensified in winter 1998 by El Nino (a warm Pacific Ocean current), stripped beaches of dunes and threatened to drown homes.

What do we do? Beach lovers are fiercely divided. On one side, homeowners, businesses, tourists, and developers want to rebuild beaches at any cost. On the other side, geologists and environmentalists claim that current methods of protecting beaches, like seawalls--walls built of wood or rocks--trigger even more erosion. The best strategy, they say, is to let nature rule.

SAVE THE SAND

For decades, Americans have put up digs by the shore, building homes, boardwalks, hotels, and entire beachfront communities. More than 50 percent of the U.S. population lives within 80 km (50 mi) of the beach. "That figure grows by 3,600 people a day," says Howard Marlowe, president of the American Coastal Coalition (ACC), a group in favor of rebuilding beaches.

But beach dwellers are paying a high price for their ocean view. Global sea levels have risen at a rate of about 15.2 cm (6 in.) in the last century. Some predict the rate will accelerate due to global warming, a gradual increase in Earth's surface temperature caused partly by burning fossil fuels like oil and natural gas. Rising global temperatures can melt glaciers and heighten the frequency of storms. The result is higher seas that batter beaches, says coastal geologist Stephen J. Leatherman, at Florida International University.

To combat rising waters, beach communities have turned to various strategies to save their sand. No method is foolproof, however; some do more harm than good.

For example: Seawalls are built parallel to the sea to protect beach houses from crashing waves. On a shore without a seawall blockade, waves naturally shift sand from one part of the beach to another. Waves also deposit sand farther inland. The process is called littoral drift. But seawalls can alter the littoral drift. When waves reach up and crash on seawalls, there's nowhere for sand to head but straight back out to sea. Result: the erosion process is accelerated.

The latest erosion-control device, called a geotube, may cause a similar threat. Huge sausage-shaped plastic tubes filled with sand are embedded in the ground to act like sand dunes. But critics argue that like seawalls, geotubes cause rapid erosion around the structure. "When you interrupt the natural movement of sand, you're going to have more erosion," says Bill Cleary, an earth-science professor at the University of North Carolina.

SAND DAMS

Other erosion solutions include jetties and groins, stone walls built on the beach perpendicular to the sea. The structures act like dams in the river of sand that moves along the shore. They trap sand on the side of the structure facing the oncoming current, thereby widening the beach.

The problem: Trapping sand on the updrift side of a jetty or groin robs sand from the other side. In fact, three groins built by the U.S. Navy in 1970 and just north of the Cape Hatteras Lighthouse caused ocean currents to scour away the shoreline near the lighthouse. The sand-stealing effects of "hard" structures like seawalls and jetties have led states like Maine, Texas, Oregon, and the Carolinas, to ban them.

One anti-erosion alternative to "hard" structures is dredging--piping in tons of sand from the seafloor 15 m (50 ft) to 4.8 km (3 mi) offshore, and spreading it onto the beach. Also known as "beach nourishment," dredging can cost more than $1 million per square mile of beach. Still, since 1965, the U.S. has spent about $1 billion to replenish more than 1,300 beaches.

Spending money on dredging saves the government money on storm damage, says ACC's Marlowe. A wider beach can better withstand a severe storm, thereby protecting homes and businesses. "We repave roads. Why not replace sand?" he says.