WALLOPS ISLAND, Virginia - Missions flown from the NASA base here have documented some of the most dramatic evidence of a warming planet over the past 20 years: the melting of polar ice, a force contributing to a global rise in ocean levels.

The Wallops Flight Facility's relationship with rising seas doesn't end there. Its billion-dollar space launch complex occupies a barrier island that's drowning under the impact of worsening storms and flooding.

NASA's response? Rather than move out of harm's way, officials have added more than $100 million in new structures over the past five years and spent $43 million more to fortify the shoreline with sand. Nearly a third of that new sand has since been washed away.

Across a narrow inlet to the north sits the island town of Chincoteague, gateway to a national wildlife refuge blessed with a stunning mile-long recreational beach - a major tourist draw and source of big business for the community. But the sea is robbing the townspeople of their main asset.

The beach has been disappearing at an average rate of 10 to 22 feet (3 to 7 meters) a year. The access road and a 1,000-car parking lot have been rebuilt five times in the past decade because of coastal flooding, at a total cost of $3 million.

Officials of the wildlife refuge say they face a losing battle against rising seas. In 2010, they proposed to close the beach and shuttle tourists by bus to a safer stretch of sandy shoreline.

The town revolted. Like many local residents, Wanda Thornton, the town's representative on the Accomack County board of supervisors, accepts that the sea is rising, but is skeptical that climate change and its effects have anything to do with the erosion of the beach. As a result, "I'm just not convinced that it requires the drastic change that some people think it does," she said.

Four years on, after a series of angry public meetings, the sea keeps eating the shore, and the government keeps spending to fix the damage.

Wallops officials and the people of Chincoteague are united at the water's edge in a battle against rising seas.All along the ragged shore of Chesapeake Bay and the Atlantic coast of the Delmarva Peninsula, north into New England and south into Florida, along the Gulf Coast and parts of the West Coast, people, businesses and governments are confronting rising seas not as a future possibility. For them, the ocean's rise is a troubling everyday reality.

This is the first in a series of articles examining the phenomenon of rising seas, its effects on the United States, and the country's response to an increasingly watery world. Other stories will show how other nations are coping.

In cities like Norfolk, Virginia, and Annapolis, Maryland, coastal flooding has become more frequent. Beyond the cities, seawater and tidal marsh have consumed farmland and several once-inhabited islands. Here in Accomack County alone, encroaching seawater is converting an estimated 50 acres (20 hectares) of farmland into wetlands each year, according to a 2009 Environmental Protection Agency study.

"It breaks my heart to think about it," said Grayson Chesser, a decoy carver whose ancestors arrived in the Chesapeake Bay area four centuries ago. He lives outside Saxis, a town that's losing ground to the water. Some nearby villages have disappeared altogether. "You've got to deal with the fact that it's happening - and what are you going to do with those of us on the edge?"

It's a question the U.S. government is dodging. More than 300 counties claim a piece of more than 86,000 miles (138,000 km) of tidal coastline in the United States, yet no clear national policy determines which locations receive help to protect their shorelines. That has left communities fighting for attention and resources, lest they be abandoned to the sea, as is playing out in Chincoteague.

"If we can't make a decision about rising sea level in a parking lot, we're in trouble as a nation," said Louis Hinds, former manager of Chincoteague National Wildlife Refuge.

Tidal waters worldwide have climbed an average of 8 inches (20 cm) over the past century, according to the 2014 National Climate Assessment. The two main causes are the volume of water added to oceans from glacial melt and the expansion of that water from rising sea temperatures.

In many places, including much of the U.S. Eastern Seaboard, an additional factor makes the problem worse: The land is sinking. This process, known as subsidence, is due in part to inexorable geological shifts. But another major cause is the extraction of water from underground reservoirs for industrial and public water supplies. As aquifers are drained, the land above them drops, a process that can be slowed by reducing withdrawals.