The next time you’re at the ocean, scoop up a handful of sand and try to imagine how it got there. Its journey may have begun millions of years ago, when a melting glacier  freed small bits of rock from a mountainside and swept them downhill, grinding the material into finer and finer particles. Rain, rivers, and gravity continued its downward path until each grain arrived at the beach.

But it’s also possible that this narrative unfolded with the help of machines—dredges, pumps, barges, and bulldozers. Many coastal beaches in the United States, including several in the National Park System, contain sand that was scoured from ocean bottoms or channels. Millions of tons of such sediment have been deposited at Cape Hatteras National Seashore, Assateague Island National Seashore, and other coastal parks, a procedure called beach nourishment or sand replenishment. Why? Because beaches erode—a consequence of nature and, often, people’s attempts to tame nature.

“Erosion is a pervasive activity throughout the park system,” says Rebecca Beavers, coordinator of coastal geology for the National Park Service. “And I don’t think it’s gotten the public attention it deserves.”

But that may be about to change in coming years, as sea levels rise and shoreline erosion becomes a more pressing concern. If storms increase in strength and frequency, as scientists have projected, coastal parks will become more vulnerable. “Pick any low-lying national park unit that has a fairly rapid relative rate of sea-level rise, and you can draw a bull’s eye,” says Robert Thieler, a research geologist with the U.S. Geological Survey. (For more, see NPCA’s recent report, Unnatural Disaster, at
www.npca.org/globalwarming.)

In response, the Park Service is focusing more intently on understanding why shorelines change and the proper response. As part of that effort, Beavers is overseeing an inventory of all the beach-nourishment projects that have taken place in the parks, as well as all the instances of coastal engineering, which include the construction of jetties, bulkheads, seawalls, and other structures designed to buffer properties from the sea or prevent erosion.

Yet the issue of how—or whether—the Park Service should respond to coastal erosion is rarely simple and often contentious. The details vary from park to park, depending on factors such as geography and history, but in every case, shoreline erosion begins with the same geological fact: Beaches move. Anywhere that land meets ocean, you can be sure that waves, currents, and wind are constantly resculpting the shape of the shoreline. On the barrier islands that line the Atlantic and Gulf coasts, storms cause waves to wash over the land and push sand toward the sound, or interior side. Over time, the island rolls over itself, growing on its sound side and retreating on its ocean side.

This natural “shoreline retreat” becomes “erosion” only when people build things in the path of a beach’s migration. In addition, structures intended to protect shorefront properties (such as seawalls and breakwaters) or to prevent sand from filling in shipping channels or drifting off beaches (such as jetties and groins) can actually expedite erosion elsewhere. “It happens everywhere along the coast; wherever there is a structure—a seawall, a groin, a jetty—there is always a downdrift effect,” says Norb Psuty, a Rutgers University geomorphologist.

Take the case of the Sandy Hook unit of Gateway National Recreation Area, a peninsula of land that juts out from northern New Jersey. In 1972, only a few years after the park was created, erosion troubles appeared at the southern end. Bathhouses and a parking lot were undermined. A septic tank, once buried, seemed to rise from the earth. Eventually, storm tides tore apart large segments of the park’s main access road. “At high tide visitors had to move off the beach,” says Psuty, who has studied Sandy Hook’s geology for more than three decades.

Over the years, sand replenishment efforts placed millions of cubic yards of new sand on the beach, which continued to blow and wash away—as quickly as 200,000 cubic yards in one year, according to Psuty’s calculations. The costs were not inconsequential. Replenishing one mile of beach with dredged sand costs anywhere from $1 million to $5 million, says Andy Coburn, associate director of the Program for the Study of Developed Shorelines.

Eventually, Psuty concluded that both natural factors and coastal engineering contributed to the problem. A longshore current along Sandy Hook’s flank was sweeping sand off the peninsula’s southern end and onto its northern end—a natural phenomenon. An eight-mile-long seawall just south of the park was yet another culprit. The sand in front of the seawall had eroded away, which meant that it couldn’t absorb wave energy. With nowhere else to go, this excess wave energy concentrated farther north, that is, in Sandy Hook, where it was drastically accelerating erosion. The result of both factors was a sand imbalance: too little sand at the southern end of the park and a surplus at the other.

To try to rebalance this equation, Sandy Hook will soon introduce a new technique called sand bypassing. A high-pressure hose will spray water on the sand at the northern end of the park. A vacuum and pumps will then suck up this gruel and force it through several miles of steel pipe to be extruded on the eroding beach at the base of the park.

Planners hope the sand-slurry pipeline will have fewer environmental consequences than conventional dredging, which can harm a range of ecosystems, injuring or killing bottom-dwelling organisms that get sucked up along with harvested sediment, says Coburn. “We’ve seen shells, rocks, live ammunition, and chopped-up turtles pumped onto the shore.”

Sand bypassing won’t necessarily work for every park with an erosion problem; other coastal parks are experimenting with their own erosion strategies. Several of these involve fine-tuning the methods of beach nourishment. At Gulf Islands National Seashore, for instance, officials are planning to conduct a sand replenishment project in two segments rather than as a single deposit to see whether such a phased approach harms fewer beach-dwelling organisms.

Technical hurdles aren’t the only challenge parks face in responding to erosion. They also face difficult philosophical decisions.

The Park Service has a mandate to conserve the parks’ natural and historic resources, and at the same time must provide for the public’s “use and enjoyment” of the parks. Those mandates often compete. So when ocean waves start eating away at a popular recreational beach, does the Park Service let nature take its course, or try to shore up the beach with new sand? When waves start lapping at a park lighthouse, does the park let the lighthouse fall or try to move it?

The Park Service generally prefers to let natural processes continue without interference, according to Julia Brunner, policy and regulatory specialist in the Park Service’s Geologic Resources Division. But, she adds, management guidelines allow parks to intervene if a park’s cultural resources are in peril or in response to erosion brought about by previous human interference, as was the case at Sandy Hook. The Park Service often works closely with the U.S. Army Corps of Engineers in deciding how to respond to shoreline erosion.

Despite such policies and guidelines, shoreline issues in the parks have spawned many long and heated debates, such as a recent argument over the fate of roads on Gulf Islands National Seashore’s Santa Rosa Island in Florida.

One of the roads leads to the Fort Pickens area—the site of prime beaches, a campground, and a historic military fort. Unfortunately, its sugar-white beaches and emerald-green waters lie in a hurricane target zone. Once set back from the Gulf, the Fort Pickens Road now lies in the surf zone, large chunks of its asphalt rent or completely gone. A second road is in similar condition. Both were victims of Hurricane Ivan in 2004 and subsequent storms the following year. Afterward, the park saw visitor numbers plummet from about 5 million to fewer than 2 million.

So the Federal Highway Administration proposed armoring vulnerable portions of the roads with concrete pavers, steel cable, or other hardened structures, at an estimated cost of $40 million. Gulf Islands Superintendent Jerry Eubanks endorsed this plan, eager to restore access to the Fort Pickens area, one of the most popular visitor destinations in Gulf Islands.

But conservation groups including NPCA and coastal scientists opposed the plan, arguing that even an armored road would almost certainly succumb to future storms. The U.S. Fish and Wildlife Service also objected to the plan, asserting that hardened structures would prevent storm-fueled tides from washing over the island, a process that creates critical habitat for many beach species including the threatened piping plover.

The conflict was finally resolved this past March: The road will not be armored; instead, damaged sections will be patched with a low-cost adhesive and asphalt, and portions of the Fort Pickens Road will be realigned farther inland. Gulf Islands is also exploring the option of offering ferry service to Fort Pickens.

The plan acknowledges that the roads might be sacrificed in a future storm, says Rick Clark, the park’s chief of science and resources management. But for now, repairing the roads and moving them as necessary is a better use of taxpayer money. Nevertheless, the past few months have been challenging, says Clark. “By virtue of the Park Service mission, we have an obligation to provide reasonable access for visitors. We can’t just say, ‘Here today, gone tomorrow.’

“On the other side, people need to recognize that these areas are vulnerable. To be good stewards, we need to take actions that will not jeopardize species, especially those that are threatened, because this may be the only habitat left to them. It’s a delicate balance, and the park’s been right in the middle.”

Above all of the challenges that shifting shorelines pose to parks is the threat of rising sea levels. Seas have risen one foot in the past century and are continuing to climb, a consequence of a warming climate. The Park Service has started to plan for this situation by assessing which parts of coastal parks would be most vulnerable. With the U.S. Geological Survey, it has created a tool called the coastal vulnerability assessment index. The instrument reveals, mile by mile, the risk posed to each section of a park. In a follow-up study, the team is determining which cultural resources—such as forts and lighthouses—are most likely to be harmed by rising seas.

The tools will help park planners identify the areas that most need protection from erosion, says Beavers, the coastal geology coordinator. Or they might lead managers to consider more drastic measures, such as abandoning some parts of a park or moving certain structures out of harm’s way, as the Park Service once did with the Cape Hatteras Lighthouse. “Coastal changes are already affecting how we can access our parks and how we can use them,” says Beavers. And rising tides will make these issues even graver.

Moving a Lighthouse

Since 1870, the Cape Hatteras Lighthouse on North Carolina’s Outer Banks has warned sailors of the pounding waves and treacherous shoals of the area that came to be called the “Graveyard of the Atlantic.” By the time Cape Hatteras National Seashore was authorized in 1937, the lighthouse itself was in danger, threatened by the rapidly approaching sea. Erected 1,500 feet from the shoreline, the structure was now only 100 feet from the sea.

Some parks have responded to encroaching shorelines by converting parts of their infrastructure into portable facilities. At the highly dynamic southern end of Assateague Island National Seashore, for example, bathrooms and shower stalls are designed to be quickly cut from their plumbing and trucked inland whenever a serious storm approaches. The park also has roads and a parking lot built from clamshells and clay, materials that can be easily replaced or moved as the shoreline changes.

It’s one thing to pick up a portable shower, but can a 2,800-ton lighthouse be moved?

Many people didn’t think so, says Orrin Pilkey, a professor emeritus of geology at Duke University. And many did not want to try, fearful that any attempt to relocate the lighthouse would destroy it. The prominent diagonal stripe running along the building’s length made it an icon of the Atlantic Coast, earning it a spot on the National Register of Historic Places.

For decades, groups had tried numerous strategies to protect the lighthouse from erosion. They had constructed groins from sheet pile, built barrier sand dunes, pumped dredged sand onto the beach, and even placed plastic seaweed in the water to buffer the waves. Nothing worked for long.

In 1988, the National Academies of Sciences and of Engineering concluded that the best way to save the lighthouse would be to move it inland. But it would take another decade to overcome protests from groups that favored more erosion-control measures.

Finally, in 1999, engineers constructed a two-foot-deep gravel road covered by thick steel mats leading from the lighthouse to its inland destination. Workers used 112 heavy jacks to hoist the lighthouse onto a raft made of steel beams and used push-jacks to move the structure along steel tracks. The half-mile journey took 23 days and cost $12 million.

To Pilkey, who has written about the event in The Earth Around Us, moving the lighthouse was the only logical thing to do. “All other solutions wouldn’t have worked, over generations,” he says. “Nature bats last at the shoreline.”