(Bloomberg) — The warming Atlantic Ocean has raised therisk of another Hurricane Sandy.

And still, trillions of dollars of real estate andinfrastructure near the shores of New York City and northern NewJersey remain vulnerable to devastation.

A storm-surge barrier similar to those in Louisiana and parts ofEurope might protect the area, but politicians have questioned its$30 billion cost, effectiveness and environmental impact. A groupof scientists, planners and property owners is urging the U.S. Army Corps of Engineers to accelerate itsstudy of the project. It may take another hurricane to speed up theprocess.

Danger of rising sea levels increases

“The danger is increasing as the sea level rises,” saidMalcolm Bowman, an oceanographer at the StateUniversity of New York at Stony Brook, who is among the group.“It won't take a monster storm like Sandy to devastate theregion.”

Bowman warned of a catastrophic storm as far back as 2005, in aNew York Times Op-Ed article. Seven years later, Sandy struck theregion, flooding airports and tunnels and ravaging shorecommunities from Atlantic City, New Jersey, to Bridgeport,Connecticut. It caused $68.9 billion in damage, making it thesecond-costliest storm in U.S. history after Katrina, according tothe National Oceanic and Atmospheric Administration.

Push for 5-mile retractable storm-surge barrier

Bowman's group is pushing for an evaluation of a 5-mile(8-kilometer) retractable storm-surge barrier at the mouth of NewYork Harbor from the Rockaways to New Jersey's Sandy Hook. That,and another smaller structure at the western edge of Long IslandSound, could protect about 800 miles of shoreline from PortElizabeth, New Jersey, to the Bronx, Bowman says.

As Bowman describes it, before a major storm, barriers wouldrise from the seabed or close in a gate-like structure to deflectthe force of a wind-blown surge, as occurred with Sandy.

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“You have to allow for marine traffic and the daily flow of thetides to flush out the harbor,” Bowman said, “But when a storm isforecast with enough wind at high tide to create a surge, you closethe gates or raise it from the seabed so water that wants to flowinto the harbor can't.”

Studying studies

Weeks after Sandy, New York Governor Andrew Cuomo said hisadministration planned to talk with city and federal officialsabout the possibility of installing storm-surge barriers. Corpsengineers, in discussions with New York and New Jersey since lastAugust, are still studying what protection strategies merit furtherstudy.

“At this point, it is premature to say whether broad-scalesolutions such as that advocated by this group, or other moreregional or localized potential solutions will fare best,” saidCorps spokesman Hector Mosley.

Piecemeal jobs

In the meantime, the state has moved ahead with a $616 millionplan for Staten Island that includes a boardwalk promenade thatwould double as a storm-surge bulwark. The Corps has that projectscheduled for completion in 2022, paid mostly by the federalgovernment.

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Billions more in federal, state and city funds are being spentalong shore areas, enhancing dunes and berms on beaches,cultivating wetlands, building walls and awarding subsidiesfor waterproofing homes and office buildings. City officialsalso envision a mostly-U.S. funded $816 million horseshoe-shapedelevated park wrapped along the southern half of Manhattan, dubbed“The Big U,” to keep out the Hudson and East Rivers.

Such localized approaches may work as well or better than amega-project, said Jainey Bavishi, Mayor Bill de Blasio's directorof the Office of Recovery and Resiliency. Her concerns about astorm barrier include cost and construction time; possibleenvironmental impact; and whether it would leave densely populatedareas of Long Island and New Jersey vulnerable, and perhaps evenmore exposed to flooding from displaced water.

“A harbor barrier is not the silver bullet,” Bavishi said.

Technology holds promise to prevent flooding

Many of these issues have been solved with barriers that protectlow-lying populations around the world, said Robert Yaro, formerpresident of New York's Regional PlanAssociation. Its retractable feature would allow for marinetraffic and tidal flow, minimizing impact to sea life and waterquality, he said. The technology holds the promise of protectingthe region for catastrophic floods for the next 150 years, Yarosaid.

“The Dutch have used this engineering for decades and barrierscurrently protect New Orleans, Stamford, Providence, London and St.Petersburg, Russia,” Yaro said. “We in New York are far behind andamong the cities on Earth we have the most to lose.”

Yaro and Bowman were among several advocates promoting the idealast month at an all-day conference in lower Manhattan attended by250 municipal bond investors, real estate developers, businessowners, insurance companies, and planners.

Lessons learned

They heard Andrew Kopplin, former director of theLouisianaRecovery Authority, describe how in New Orleans after Katrina,a bipartisan coalition of elected officials and business leaderspersuaded Congress to approve a $14.5 billion system of levees anda storm-surge barrier. The barrier, a 1.8-mile array of gates,protected the city from Hurricane Isaac's landfall in 2012, saidKopplin, now president and chief executive officer of the GreaterNew Orleans Foundation, a non-profit charitable civic group.

Related: 12 ways the U.S. is using nature to protect againstnatural disasters

“It was simply a matter of political will,” he said.

Officials in the Cuomo and de Blasio administrations say theyawait the Corps' findings.

“We clearly want to see the New York Harbor barrier studied,”said James Tierney, Cuomo's deputy environmental commissioner forwater resources. “The process requires a full-blownfeasibility study. The Army Corps process is what we have to livewith.”

Residents worry about next big storm

Marco Pasanella, 54, who lives above his gourmet wine shop onlower Manhattan's South Street that got flooded when Sandy hit,says the pace and scope of government response has beendisappointing.

He says he's seen no measures that would protect hisneighborhood if another storm hit. The National Oceanic and Atmospheric Administration haspredicted as many as 17 tropical storms, about five more thanaverage, may hit the Atlantic coast this year.

“The decisions have Balkanized the neighborhoods with apiecemeal approach, just a series of uneven, irregular blockadesthat will not stop the water from finding its way ashore,”Pasanella said.

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Across Manhattan at Chelsea Piers, a recreational facilitysituated over the Hudson, Michael Braito, the property's chiefengineer, said neighborhood protections won't be enough to stopstorm-surge water coursing through his building.

“These piecemeal fixes buy little more than peace of mind,”Braito said. “It's like a boat with 100 holes and we've patchedhalf of them and we're going to sink. They need to thinkbigger.”

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