From his government office in Virginia Beach, Clay Bernick can see the future, and that future looks a rather lot like the movie “Waterworld.”

The sea level is rising in Virginia Beach and the entire area known as Hampton Roads because of the warming climate, and the area also happens to be sinking for other geological reasons.

Within 50 years, a big part of Virginia Beach’s identity — its beach — could be lost if nothing is done, said Bernick, the city’s environment and sustainability administrator. Large pieces of land could also be lost to the ocean in Norfolk within a few generations.

In fact, the National Oceanic and Atmospheric Administration warns that, outside of greater New Orleans, Hampton Roads is at the greatest risk from sea-level rise for any area its size.

“It’s a significant threat,” Bernick said. “At this point, I wouldn’t put it in the category of fear, because it’s a long way off.” But he added: “You’ve got multiple factors with flashing lights saying, ‘Okay, guys, what are you going to do?’ ”

To help answer that question in the past, municipalities turned to a manual published by the Army Corps of Engineers since 1954 on how to protect shores by holding back the sea.

But earlier this month, the U.S. Environmental Protection Agency published the first manual on how not to hold it back, arguing that costly seawalls and dikes eventually fail because sea-level rise is unstoppable. The federal Global Change Research Program estimates that the sea level will rise 14 to 17 inches in the next century around Hampton Roads.

The analysis, “Rolling Easements,” published on the EPA’s Web site, hopes “to get people on the path of not expecting to hold back the sea” as the warming climate is expected to melt ice around the globe, EPA researcher James G. Titus said.

Titus said state and local governments should start crafting laws and ordinances to limit development on vulnerable lands and encourage people living there to move inland. Reflecting the scale of the problem, the Hampton Roads Planning District Commission issued a report this month warning that 1 million residents would now be threatened by a Category 4 hurricane.

The EPA report said governments have three options to deal with sea-level rise: They can stay on the well-worn path of building expensive protection and raising streets and buildings. They can beat an organized retreat from the shore, perhaps by offering financial incentives to people and organizations to move inland. Or they can allow people to do whatever they want for their waterfront properties but tell them in no uncertain terms that they are on their own when the waters rise.

In Hampton Roads, planners and environmentalists said the EPA recommendations are on the table. Bernick called the report “useful.” John Boon, a professor emeritus at the Virginia Institute of Marine Science who has studied sea-level rise for years, called it “very well reasoned.”

Most people aren’t taking the threat of sea-level rise decades from now too seriously, but planners say it is worrisome when you consider what’s at stake — public roads, schools, bridges, tunnels, museums, police stations and housing developments that are built to last well beyond the average 30-year home mortgage.

“It could result in those things having a life span less than what we budgeted for,” said John Carlock, deputy executive director of the Hampton Roads Planning District Commission. “That part of it is trying to make wise use of taxpayer funds.”

Cities such as Norfolk have already experienced the effects of sea-level rise as powerful storms pushed water inland, leading to flooding in places where it once was rare.

In a report this month, “Preparing for the Changing Climate,” the group Clean Air Cool Planet wrote that the increased flooding was inevitable along the Atlantic coast because the number of federally declared storms has increased — up by 50 percent over 20 years, for instance, in New England.

“In New Hampshire alone, the costs associated with declared storm damages have increased nearly 15-fold and the state has suffered through four ‘100-year floods’ in the last decade,” the report said.

Seven hundred miles south of New Hampshire, Hampton Roads is even more vulnerable because several rivers run through it on their way to the Chesapeake Bay and eventually the Atlantic Ocean. Its dense population of about 2 million residents swells with summer vacationers, making it “the largest urban concentration south of the Northeast until you get to Florida,” Bernick said.

Unfortunately, this crowded, low-lying area also has long-term geological issues to deal with. Thirty-five million years ago, a meteor landed relatively close by and created the Chesapeake Bay Impact Crater. Hampton Roads is also home to a downward- pressing glacial formation created during the Ice Age. Scientists theorize that these ancient occurrences are causing the land to sink — and together account for about one-third of the sea-level change.

But human nature leads to rebuilding flooded areas however risky that might be, rather than leaving them.

“Unfortunately, we have a major storm like Hurricane Isabel and a lot of homes are flooded and people feel the economic impact,” said Boon, the professor. In response, city leaders hustle to protect shores in a way “that’s not very well thought-out,” he said.

A few years ago the city spent $1.5 million to elevate some homes in the Larchmont area, knowing the water will probably crawl to their doorsteps again.

If this keeps up, insurance rates will skyrocket as storms sweep the rising seas onto roads and inside people’s homes and businesses.

Building walls to protect development will cost a fortune, said James V. Koch, a professor of economics at Old Dominion University. Koch said the average cost of erecting a dike is about $35 million per mile.

“Norfolk has a little bit of that now,” Koch said of the city’s defenses, “but they’re not very well protected.”

A rise of a few inches will cause significant problems, Koch said, because much of Hampton Roads, including the Navy base, is at sea level.

In fact, two-thirds of the economy of Hampton Roads is based on “things significantly related to sea rise,” Koch said, and most especially Virginia Beach. A sustained rise in sea levels would be “a big thing” for the beach and those who make a living off it, Koch said.

Koch proposes one possible solution: “They have to think about moving back hotels or raising them up to make it possible to maintain a tourist presence.”