Hurricane Sandy caused massive destruction when it hit Hoboken, N.J., in October 2012. The city is now trying to decide how best to defend against future such storms. (Eduardo Munoz/Reuters)

The tavern that Tom Brennan has run for decades sits two blocks from the waterfront here, with views of the gleaming Manhattan skyline across the Hudson River.

Like much of Hoboken, his business was devastated four years ago when the massive storm surge from Hurricane Sandy filled this city like a bathtub, knocking out the power grid, swamping train tunnels, stranding residents, flooding homes and causing hundreds of millions of dollars in damage.

But unlike most of Hoboken, Brennan’s tavern would remain unprotected by the leading proposals to defend against the next superstorm. Some of his neighbors are content to stay outside the proposed barriers, saying they would rather take their chances than risk changes that might alter the city’s historic charm. Brennan isn’t one of them.

“What are you going to do for me? What are you going to do for [the] other people?” he asked at a recent community meeting, adding later, “I’m not looking for a handout. I’m just looking for answers.”

For months, the question over how best to fortify Frank Sinatra’s home town has provoked division, hard feelings and debate — about what to protect and what to leave exposed, about where barriers should and shouldn’t go. Those tensions foreshadow the tough choices an increasing number of cities will face in an age of climate change, rising seas and more frequent and powerful natural disasters.

In the wake of Hurricane Sandy, a resident walks through floodwaters in Hoboken. (Emile Wamsteker/Bloomberg News)

Nearly 1.9 million U.S. homes could be rendered uninhabitable if sea levels rise six feet by the end of the century, as many scientists expect, according to a report from the real estate data firm Zillow. Nearly half could be in Florida, but New York, New Jersey, South Carolina and Louisiana each could have tens of thousands of inundated homes.

“The places that are struggling with this early, like South Florida or Hoboken, are just harbingers of the future for almost any coastal city,” said Benjamin Strauss, director of the program on sea-level rise at Climate Central, an independent organization of scientists based in New Jersey. “Every place is going to have to make decisions about what they can protect and what they can’t.”

Most will not start with the advantage that Hoboken has, in the form of a $230 million federal grant awarded in 2014 to keep the river at bay and protect low-lying areas here and in nearby Jersey City and Weehawken.

Early conceptual ideas included barriers along parts of Hoboken’s cherished waterfront — and, in one case, down a leafy residential street lined with brownstones. The backlash came quickly.

“When people heard the word ‘walls,’ they just thought, ‘Hoboken can’t have walls,’ ” said Brian Battaglia, owner of a home-furnishings store who supports the flood-protection efforts. “They went ballistic. . . . There was a lot of yelling in the early days.”

Although Sandy might be a hundred-year storm, encroaching waters already are threatening some cities. The East Coast, from Massachusetts south, is particularly at risk. Norfolk, for one, has debated many strategies, from building floodgates to abandoning the most vulnerable parts of town. Miami Beach is spending $400 million to install pumps and raise sea walls and roads in a bid to stave off encroaching water.

Many others are sure to face a similar reckoning in coming decades, scientists say.

“There will be a bitter awakening,” said Klaus Jacob, a Columbia University climate scientist and disaster expert who predicted much of the damage a storm like Sandy would do to New York City. “Right now, the policy [in many places] is postponing the solution for future generations. It’s an injustice.”

Despite the conflicts that have surfaced in Hoboken, the city is ahead of the curve in trying to adapt, said Michael B. Gerrard, a Columbia Law School professor and director of the Sabin Center for Climate Change Law.

“Hoboken is taking proactive measures to protect itself, which relatively few places are doing,” Gerrard said. “They are seeing the hurdles that cities all over the world will face when they tackle this problem.”

The densely packed city of 50,000 also starts with a natural advantage. Because it covers only about a square mile, experts say that relatively modest measures to prevent storm surges on its north and south sides could protect a large swath of the population.

“If there’s a city along the Atlantic coast in which a sea wall — or, I should say, a protective structure — is warranted, Hoboken can probably make the best case for it,” Jacob said. “You get a lot of bang for the buck.”

Or, as Strauss said, “If it can’t happen in Hoboken, it can’t happen anywhere.”

It still hasn’t happened here, at least not yet. Early on, hundreds of residents packed public meetings. Some started a Change.org petition and created a Facebook group called Save Our Streets. They barraged the state’s Department of Environmental Protection with angry letters and emails, calling the effort “ridiculous,” “half baked” and “short-sighted.”

“Please do not destroy one of the most valuable assets Hoboken has, which is its view and the charm of tree-lined streets,” one resident wrote.

“To have the waterfront ruined by these walls is absolutely unimaginable,” wrote another. “You have to do better.”

“I view this project as a poorly designed overreaction to low-probability events,” wrote another.  

Much of that outrage appears to have dissipated, as officials tweaked the initial designs and abandoned the most controversial features.

“Part of it was trying to get people to understand we’re talking about something that’s beautifully designed and landscaped,” Mayor Dawn Zimmer said. One proposal would disguise a large barrier as a boathouse, for example. “That’s extremely important to me. . . . We’re not going to be building ugly walls.”

After the many meetings and changes, a mayoral listening tour and vows that any new flood-fighting structures would blend in, officials are poised to settle on a specific engineering approach in coming weeks.

Several proposals are on the table, and each includes strategies for pumping out rain and floodwater and for slowing their release into the city’s aging sewer system. The leading contenders would protect about 85 percent of the city from a Sandy-like storm surge, with some waterfront buildings left outside of the barriers.

An intense design phase will take more than a year, and the goal is to finish construction no later than 2022.

“This is not an easy project for the city. I think they’ve done a good job listening to folks and incorporating feedback,” said Joseph Calabrese, who lives in Harborside Lofts, which overlooks the water and would be in the 14 percent of the city left unprotected, along with Brennan’s tavern. “I’d prefer not to be protected directly and to preserve the waterfront.”

For some residents, particularly those who found themselves underwater after Sandy, the first priority is to avoid a repeat of that disaster.

“There are plenty of places to go look at a view, but you have to think, it’s these people’s lives,” said Tracey Lyons, who lived in a public housing project off Jackson Street that experienced some of the worst flooding. Backed-up sewage filled her bath and sinks, and she waded through knee-deep water outside her first-floor apartment.

“It was horrible. [The streets] looked like Venice,” said 83-year-old Rose Visaggio, who lost furniture, family photos and other keepsakes when the bottom floor of the Adams Street home where she has lived for more than a half-century filled neck-deep. “We need protection. We need to do something.”

On a recent evening at the Stevens Institute of Technology, a standing-room-only crowd gathered to see computer simulations of how the remaining designs would safeguard Hoboken should another massive hurricane strike.

Some residents expressed lingering doubts that the project will save the city. Others said too many questions are still unanswered.

Yet most seemed to acknowledge that Hoboken will become only more vulnerable over time.

“We should be very critical of this process, that’s fair. But the idea of not doing anything is unfathomable to me — it ain’t going to get better,” said Gary Holtzman, a member of the planning board. “I’m willing to give up a little bit of my view or complete access to the waterfront to get a benefit out of it. . . . It’s not the Berlin Wall.”

The meeting ended near sunset. Outside, Manhattan shimmered in the distance. Mayor Zimmer said she understands the fear of change, the disagreements over specific plans, the impulse to guard Hoboken’s character. But she also remembers the damage Sandy did.

“People’s whole lives were on the sidewalk,” she said. “It was devastating.”

And she knows the water, so calm on this summer night, will rise again.

“There’s a clear misunderstanding when people think it happened once, so it’s not going to happen for another 100 years. That’s not true,” Zimmer said. “It could happen next year. And until we get this project completed, we can’t really protect our city.”