All along the narrow highway that runs through the Outer Banks, construction crews were hard at work this week, using power shovels to bolster the walls of sand that protect the road from the sea. Residents were busy with their own preparations: moving valuables to the second floor, parking cars on higher ground. Vacationers packed up and heeded government warnings to flee.

Hurricane Florence was on its way, bringing with it 140 mph winds, more than a dozen feet of storm surge and who knows how many inches of rain. Everyone knew what might happen next: The ocean could overtop the dunes and wash out the road. Water could fill homes and turn streets into rivers. Sandy beaches might vanish, oceanfront buildings might be destroyed.

By midweek, the forecasts for Florence had shifted, as forecasts often do: The worst of the storm would most probably make landfall near the border with South Carolina, about 100 miles away. The Outer Banks, maybe, would avoid catastrophe, this time. As water began to turn the streets of Cape Hatteras into a river early Thursday, the first surge and bands of the storm beginning to reach the shore, a narrow escape seemed possible.

But it is only temporary. One of these hurricanes, many worry, will expose the Outer Banks for what they have always been: “Basically just a sand bar,” in the words of John Trubich, who lives in the northern town of Kitty Hawk.

Trubich contemplated that not-so-distant future at the Food Lion as he picked up supplies to get him through the next few days.

“Mother Nature made the Outer Banks just by pushing sand around. It’ll eventually be washed away,” Trubich said. “Hopefully not in my lifetime.”

Dawn at Nags Head in the Outer Banks of North Carolina on Wednesday. Much of the Outer Banks has evacuated because of warnings about Hurricane Florence. (Steve Earley/Virginian-Pilot/AP)

The Outer Banks are a string of peninsulas and barrier islands along the North Carolina coast, 200 miles long and never more than three miles wide. They were formed over decades by the repeated movement of powerful waves across the seafloor.

But waves can also reshape them. All of the islands are slowly shifting west toward the mainland, beaten back by the encroaching sea.

These alterations are nature’s way of redistributing the tremendous energy of the ocean, explained Reide Corbett, a coastal oceanographer at Eastern Carolina University and executive director of the Coastal Studies Institute in Manteo.

“It’s a dynamic system,” Corbett said.

But now that system also sustains some 30,000 year-round residents and a billion-dollar tourism industry.

In this photo provided by DroneBase, waves crash along Avon, N.C., in the Outer Banks ahead of Hurricane Florence. (DroneBase/AP)

“As you develop, you don’t want the shoreline to change,” Corbett said. “We’ve essentially short-circuited that natural process.”

Eddie Skakle, who has lived his whole life on Hatteras Island, at the southern end of the chain, remembers watching crews build a motel on the oceanside of the island. Back then, visitors would walk 500 feet across the broad expanses of sand between the building and the water.

Today, the beach is less than a fifth that size.

“The edge of the ocean moves a little closer and a little closer every year” said Skakle, demonstrating with his hands.

Skakle is no stranger to encroaching seas. His house, built by his grandfather in 1917, had to be raised 18 inches several decades ago to handle major storms. Even so, when Hurricane Matthew hit in October 2016, it flooded his home with a foot of brackish water.

Sand dunes help dissipate the waves that would otherwise crash down upon buildings. But still, homes are lost. In Mirlo Beach, a community with a welcome sign that reads “Dare to dream the impossible dream,” three rows of homes have been lost in the past 30 years, according to Audubon magazine.

The Outer Banks’ vulnerability is especially apparent during hurricanes, when the barrier islands are the first land masses to be bombarded by water and wind coming off the Atlantic. Hurricane Isabel in 2003 cut a new inlet between the ocean and Pamlico Sound, effectively severing the southern part of Hatteras Island from the rest of the community. Skakle and his wife had to rely on a ferry service to cross the new body of water every time they wanted to go to the store or get their mail.

To prepare for Florence, they left their little skiff with friends on the other side of the island. They don’t want to be stranded again.

But a storm doesn’t have to cut a new inlet to cause trouble.

“The beach road regularly disappears,” said Pat Taylor, a Kitty Hawk resident who was stocking up on last-minute supplies at the grocery store ahead of Florence’s arrival.

“And Route 12 on Hatteras,” added her husband, Fred Wahl.

That road, NC12 — the only land link between Hatteras Island and the rest of Dare County — closed Thursday afternoon in both directions due to ocean overwash.

Taylor brought up “beach nourishment,” the practice of dredging sand from miles out in the ocean and depositing it along shorelines to mitigate erosion. Since 2011, seven beaches in the Outer Banks underwent this treatment, which helps counter erosion and protects structures that are becoming more vulnerable to storm damage as they get closer to the sea. Corbett said early analyses suggest there were fewer damage claims filed after storms in the wake of the first nourishment project in Nags Head.

But the efforts, which can cost as much as $8 million per mile of beach, are funded by an increased occupancy tax. Not every Outer Banks resident approves.

A man pushing his water-bottle-laden cart past Taylor and Wahl overheard their conversation about the program. He grimaced and yelled, “40 million dollars!” then strode away.

“Some people think you can’t keep the ocean back,” Taylor said.

At Mulligan’s Grille in Nags Head, longtime Outer Banks residents Charlie Aycock and Speight Lilley said they support the nourishment projects.

“If we let nature have its way, there’d be a lot of places we’d lose,” Lilley said. “The value to the tourist economy is worth the money.”

“Everybody here depends on tourists in some way or another,” Aycock said. “They bring the money, and God bless ‘em.”

But Skakle was skeptical. The loose sand from the nourishment treatments is easily eroded. Just weeks after the completion of a project on Buxton Beach this past spring, storm surge from a nor’easter washed over the new beach and deposited three feet of sand in a motel parking lot.

“Mother Nature always brings herself back and brings it back like it’s supposed to be,” Skakle said.

Corbett, the oceanographer, acknowledged that nourishment is “a Band-Aid” on the issue. Ultimately, he said, people on the Outer Banks will have to reconsider how to live on their changing land. One of the options might be “controlled retreat” from the oceanfront.

“After the storm moves through, when the rebuilding is done, that’s what we need to be thinking about,” he said.

He was sitting at his hurricane-ready home in Kitty Hawk, eyes on the ocean, waiting for Florence.

Kirk Ross, in Chapel Hill, N.C., contributed to this report.