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At a luxury condo building under construction in East Boston, the ground floor is being built with the expectation that ocean waters will pour through it.

Over at Suffolk Downs, developers plan to turn the old racetrack into an office campus with acres of parkland that can double as a giant moat to keep buildings high and dry.

And throughout the Seaport District and other low-lying parts of the city, developers are grappling with the notion that rising seas may someday flood the very neighborhoods that a wave of new construction is transforming.

In an attempt to fend off disaster decades from now — or even sooner — builders are raising the earth, installing extra-tall ground floors, and otherwise redoubling their flood-protection efforts. They’re hoping this array of architectural defenses will allow waterfront buildings to deal with the Atlantic Ocean, rather than be swamped by it.

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Environmentalists and urban planners say the icy floods that streamed through parts of downtown Boston last month during an unexpectedly powerful coastal storm were a sign of what climate change might mean for the city, and highlight the urgency of preparing for it sooner rather than later.

“We’ve been talking about 2030, and all these great plans for two decades from now,” said Blake Jackson, who works on sustainability at the architecture firm Stantec. “Well, 2030 just became 2018.”

That doesn’t mean anyone is considering putting a halt to waterfront development, despite projections that Boston Harbor could rise three feet — enough to make flooding routine throughout large swaths of the city — by the 2070s. Remnants of the old industrial waterfront are hot properties for luxury housing and office projects, while other vulnerable areas — from Widett Circle to Sullivan Square — have been circled by planners as prime locations for new neighborhoods.

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The city’s 2016 Climate Ready Boston plan promised defenses for critical spots in flood-prone areas, and it has begun rolling out both short- and long-term neighborhood-level strategies. The Boston Planning and Development Agency is starting to ask more about flood resiliency as it permits new buildings. And increasingly, developers — sometimes prodded by investors and insurance companies — are taking matters into their own hands, designing buildings to live with rising waters for decades to come.

Their methods are quickly evolving and becoming more innovative. When the new Spaulding Rehabilitation Hospital opened five years ago in the Charlestown Navy Yard, the decision to put electrical systems on upper floors instead of in the basement was considered somewhat revolutionary. Today, that’s standard on waterfront projects.

In East Boston, Clippership Wharf is being built with the issue of sea level rise as a concern.
In East Boston, Clippership Wharf is being built with the issue of sea level rise as a concern.Jonathan Wiggs/Globe Staff

Some are going beyond that strategy in their attempts to mitigate the effects of rising waters, like the developers of Clippership Wharf, a $225 million housing complex under construction on an East Boston pier. At low tide, a spit of land creates a “living shoreline” — an area where tidal pools form on the rocky landscape. When the sea comes in at high tide, it laps against the base of the pier, and birds perched on the remains of a sea wall that’s just beneath the surface look like they’re standing on water.

Rather than trying to wall the ocean out, developer Lendlease chose to work with it. The company is importing dirt to raise parts of the 7-acre site as high as 25 feet above sea level, while leaving lower areas to fill with water and drain with the tide. It’s also designed a 1,700-foot Harborwalk that will improve access to the water while acting as a buffer when seas get too high.

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“This is the only development site in Boston that intentionally floods every day,” said Lendlease general manager Nick Iselin. “Every day, twice a day.”

In addition, the ground level of one building is being set aside as a kayak rental center, complete with a ramp to the harbor. Built with water-resistant materials, it’s made to let sea water wash through the space in a flood. Above it sit luxury condominiums with killer views across the harbor. Two-bedroom units start at $825,000, and when 40 of the condos went on sale last summer, they sold out in a day and a half.

“We had some people ask, ‘How am I going to be protected in a storm?’ ” Iselin said. “But we also heard a lot of ‘Wow, this is awesome.’ ”

Suffolk Downs, too, is planning based on the premise that the seas will someday come. The horse track site sits between the Chelsea River and Belle Isle Marsh, with a creek running through its grassy infield. As the water gets higher over time, the land is bound to get wet. So developers at HYM Investment Group planning a huge office campus there — maybe for Amazon’s second headquarters — are siting buildings and roads on berms well above a 100-year flood plain. It will feature sprawling grassy areas and even a sunken amphitheater, aimed at holding millions of cubic feet of storm water, for days if necessary.

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“You need to raise up the site — the buildings and the roads — then shelter in place,” said HYM managing partner Tom O’Brien. “We want to be prepared for what’s coming.”

Even builders on slightly higher ground are taking precautions. The L Street Power Station, along Reserved Channel in South Boston, sits far enough above sea level that its developers don’t expect most of the site to flood any time soon. But they’re designing extra-high ceilings on the first floor of the buildings — 15 feet instead of 10 — so they can raise the floor, if necessary, keeping it dry for decades to come.

“If it turns out, 50 years from now, that the world is worse than we’d hoped, we can add a foot or two at the bottom and still have a usable floor-to-ceiling height,” said Greg Bialecki, a principal at Redgate, which is building the project. “It’s sort of a usable worst-case scenario.”

“This is the only development site in Boston that intentionally floods every day,” said Lendlease general manager Nick Iselin of the Clippership Wharf project. “Every day, twice a day.”
“This is the only development site in Boston that intentionally floods every day,” said Lendlease general manager Nick Iselin of the Clippership Wharf project. “Every day, twice a day.”Jonathan Wiggs/Globe Staff

But when it comes to floodproofing, experts say, new development is the easy part. Protecting older buildings in a city that has grown along the water for 400 years is another matter.

“Existing buildings are the $64 trillion question,” said Ruth Silman, an environmental lawyer at Nixon Peabody. “They’re very vulnerable, and much harder to rearrange.”

As older buildings in flood zones are renovated, the city is encouraging their owners to move mechanical systems to upper stories, Silman said. Occasionally, it’s possible to raise ground floors a few feet. But mainly, the focus is on preventing flooding in the first place, by raising the ground at low-lying spots — places a storm surge could overtop, swamping an entire neighborhood.

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That’s the strategy being used for “coastal resilience” plans covering East Boston and Charlestown that were issued in October as part of Climate Ready Boston. They call for measures that range from a floodwall at the mouth of the East Boston Greenway to a landscaped park behind the Schrafft’s Center in Sullivan Square. A similar plan is in the works for the Seaport and South Boston. Neighborhood groups in the downtown waterfront area, where workers at the Long Wharf Marriott built a dam out of snow to protect the hotel during last month’s flooding, also have asked the city for help.

Modifying Boston’s buildings and land so the city can withstand higher sea levels will carry a steep price. The proposals for East Boston and Charlestown alone could cost up to $260 million, the city estimates.

One possible source of funding is new development. As more waterfront projects are approved, said Jamie Fay, president of planning firm Fort Point Associates, it’s important to think about how they might help keep neighboring properties dry. For instance, a new project could raise the ground level at key spots, or developers could be required to contribute money to neighborhood-wide flood defenses as a condition of having a project approved.

“We are fortunate in that regard,” Fay said. “There is a lot of new development going on that we can leverage to help with this.”

But eventually, Jackson warned, developers — who already fund affordable housing and various community programs — could tire of footing the bill to keep neighbors dry. And, at some point, development will slow. Then what?

Jackson pointed to General Electric’s planned headquarters in Fort Point, designed to sit 4½ feet above the flood plain as a buffer for a key stretch along Fort Point Channel. It’s a great idea, Jackson said, but construction of the new building is on hold while GE sorts out the far larger financial challenges it’s facing. (Renovation of two existing buildings at the site is underway.)

“There’s a lot of promise with that building,” Jackson said. But that promise, he added, needs to translate into results — soon. In the January storm, Jackson noted, “We had a flood of water rushing [a block away] down A Street.”

That has some experts thinking about doing something more dramatic, like constructing a sea wall that would stretch 4 miles across Boston Harbor, from Hull to Deer Island. Such a wall could close during a storm and break damaging waves before they wash ashore. Researchers are just beginning to study the concept, and a wall of that size would probably cost billions of dollars. But it’s the kind of idea Boston needs to start thinking about, said Laura Marett, a landscape architect at Sasaki.

Staving off the sea, she said, requires “a combination of things. Not a singular engineering solution, but a way of figuring out how this city can live with water. It’ll be our generation’s legacy to the city.”

Clippership Wharf is one of a number of projects rising along the harbor.
Clippership Wharf is one of a number of projects rising along the harbor.Jonathan Wiggs/Globe Staff

Tim Logan can be reached at tim.logan@globe.com. Follow him on Twitter @bytimlogan.