By Justin Gillis, New York Times

NORFOLK, Va. — Huge vertical rulers are sprouting beside low spots in the streets here, so people can judge if the tidal floods that increasingly inundate their roads are too deep to drive through.

Five hundred miles down the Atlantic Coast, the only road to Tybee Island, Georgia, is disappearing beneath the sea several times a year, cutting the town off from the mainland.

And another 500 miles on, in Fort Lauderdale, Florida, increased tidal flooding is forcing the city to spend millions fixing battered roads and drains — and, at times, to send out giant vacuum trucks to suck saltwater off the streets.

For decades, as the global warming created by human emissions caused land ice to melt and ocean water to expand, scientists warned that the accelerating rise of the sea would eventually imperil the United States’ coastline.

Now, those warnings are no longer theoretical: The inundation of the coast has begun. The sea has crept up to the point that a high tide and a brisk wind are all it takes to send water pouring into streets and homes.

Federal scientists have documented a sharp jump in this nuisance flooding — often called “sunny-day flooding” — along both the East Coast and the Gulf Coast in recent years. The sea is now so near the brim in many places that they believe the problem is likely to worsen quickly.

These tidal floods are often just a foot or two deep, but they can stop traffic, swamp basements, damage cars, kill lawns and forests, and poison wells with salt. Moreover, the high seas interfere with the drainage of storm water.

“Once impacts become noticeable, they’re going to be upon you quickly,” said William V. Sweet, a scientist with the National Oceanic and Atmospheric Administration in Silver Spring, Maryland, who is among the leaders in research on coastal inundation. “It’s not a hundred years off — it’s now.”

Local governments, under pressure from annoyed citizens, are beginning to act. Elections are being won on promises to invest money to protect against flooding. Miami Beach is leading the way, increasing local fees to finance a $400 million plan that includes raising streets, installing pumps and elevating sea walls.

In many of the worst-hit cities, mayors of both parties are sounding an alarm.

“I’m a Republican, but I also realize, by any objective analysis, the sea level is rising,” said Jason Buelterman, the mayor of tiny Tybee Island, one of the first Georgia communities to adopt a detailed climate plan.

But the local leaders say they cannot tackle this problem alone. They are pleading with state and federal governments for guidance and help, including billions to pay for flood walls, pumps and road improvements that would buy them time.

Yet Congress has largely ignored these pleas, and has even tried to block plans by the military to head off future problems at the numerous bases imperiled by a rising sea. A Republican congressman from Colorado, Ken Buck, recently called one military proposal part of a “radical climate change agenda.”

As the problem worsens, experts are warning that national security is on the line. Naval bases, in particular, are threatened; they can hardly be moved away from the ocean, yet much of their land is at risk of disappearing within this century.

“It’s as if the country was being attacked along every border, simultaneously,” said Andrea Dutton, a climate scientist at the University of Florida and one of the world’s leading experts on rising seas. “It’s a slow, gradual attack, but it threatens the safety and security of the United States.”

‘We’re Living It.’

One night eight years ago, Karen Speights, a Norfolk resident, was sitting at the dinner table with her mother, eating crab legs dipped in butter and a tangy sauce. She felt a tingle.

“Ma!” she cried. “My feet are wet!”

Her mother laughed, but then she felt it, too: a house that had not flooded since the family moved there in 1964 was soon awash in saltwater. Speights initially hoped that flood was a fluke. Instead, it turned out to be the first of three to hit their home in less than a decade.

Nowadays, Speights, an administrative worker at a utility company, is wondering how to get her and her mother out of the neighborhood before the water comes again, without taking too much of a financial hit. And she pays more attention to problems that once seemed remote, like warnings from scientists about the rising sea.

“I believe it because we’re living it,” Speights said as she sat on her sofa, nodding toward the nearby tidal marsh that sent water into her living room. “The water has to be rising if we never flooded, and all of a sudden we’ve flooded three times in eight years.”

Because the land is sinking as the ocean rises, Norfolk and the metropolitan region surrounding it, known as Hampton Roads, are among the worst-hit parts of the United States. That local factor means, in essence, that the region is a few decades ahead in feeling the effects of sea-level rise, and illustrates what people along the rest of the coast can expect.

The biggest problems involve frequent flooding of homes and roads. As the sea rises, hundreds of tidal creeks and marshes that thread through the region are bringing saltwater to people’s doorsteps.

This summer, on a driving tour of Norfolk and nearby towns, William A. Stiles Jr. pointed to the telltale signs that the ocean is gradually invading the region.

He spotted crusts of dried salt in the streets, and salt-loving marsh grasses that are taking over suburban yards. He pointed out trees killed by seawater. He stood next to one of the road signs that Norfolk has been forced to install in recent years, essentially huge vertical rulers so people know the depth of floodwaters at low-lying intersections.

“There’s just more and more visible impacts: water on the street, water that won’t clear from the ditch, these intense rain events, higher tides,” Stiles said.

“It’s beginning to catch the attention of citizens, restaurant owners, business people, politicians. There’s just much more of a conversation, and it’s not just in the politically safe places. It’s everywhere.”

The Obama administration has been pushing federal agencies, including the Pentagon, to take more aggressive steps. But without action in Congress, experts say these efforts fall far short of what is required.

In South Florida, among the worst-hit parts of the country for sunny-day flooding, people are not waiting for state or federal help. Those who can afford it are starting to act on their own. A company, Coastal Risk Consulting, has cropped up to advise them, and is offering its services nationally.

In Miami Beach and Fort Lauderdale, as well as in older Northern cities like Boston and New York, tidal marshes and creeks were filled in a century or more ago to make new land, and it is in these areas — “back bays,” as some of these spots are called — where the flooding is happening first.

That is because they remain the lowest spots in the landscape, vulnerable to the rising water nearby. Old drain pipes empty into the tidal creeks, and at high tide the water can back up through these pipes, bubbling into the streets seemingly from nowhere.

In Miami Beach, city engineer Bruce A. Mowry has come up with a plan for combating the flooding. He rips up problematic streets, raises them with extra dirt and repaves them, installing new drains and giant pumps that can push water back into the bay. The approach has already been shown to work in several neighborhoods.

A controversy has erupted about whether Miami Beach is polluting Biscayne Bay with the water, but the city is pushing ahead. Miami Beach plans to spend at least $400 million on its plan by 2018.

The huge county government for the region, Miami-Dade County, is developing its own resilience strategy, one likely to cost billions. It has committed to rebuilding some of its decaying infrastructure, like a sewage plant, in a way that safeguards against sea-level rise and storm surges.

“I don’t see doom and gloom here; I see opportunity,” said Harvey Ruvin, the clerk of courts for Miami-Dade County, who has been a leading voice on the environment in Florida for a half-century, and who recently led a county task force on sea-level rise. “We’re talking about the most robust possible jobs program you can think of, and one that can’t be outsourced.

To Learn More:

Climate Change Denier Trump Cites Global Warming as Reason to Build Wall to Protect His Luxury Golf Course (by Michael Biesecker, Associated Press)

Rising Sea Levels May Disrupt Lives of 13 Million Americans (by Tatiana Schlossberg, New York Times)

Global Warming Sends Earth’s Sea Levels Rising Faster than Any Time in Past 2,800 Years (by Seth Borenstein, Associated Press)

Miami and New Orleans among 400 U.S. Cities said to be Doomed by Rising Sea Levels (by Noel Brinkerhoff, AllGov)

$40 Billion in U.S. Coastal Park Assets Are at “High Risk” from Rising Seas (by Ken Broder, AllGov California)

Scientists Predict 4 Million Americans will be “Significantly” Affected by Rising Sea Levels within 6 Years (by Noel Brinkerhoff and Steve Straehley, AllGov)

1,700 U.S. Cities Could Be Partially Underwater by 2100 Due to Climate Change (by Noel Brinkerhoff, AllGov)