Long Island is changing, nowhere more so than on our coastline. Water and wind continue to sculpt our land.

We have not always responded well. We pump sand onto our beaches, watch it wash away, then pump sand again. We build too close to the water’s edge, despair when the sea rushes in, then build again. We protect one part of our shoreline with bulkheads and groins, see how that damages other parts of the shore, then remake those very same structures when they weaken.

It’s time to reconsider what we’ve always done.

That became imperative after superstorm Sandy in 2012. Climate change is causing sea levels to rise and spawning more frequent bursts of extreme weather. We’ve seen the damage that can result.

The threat of water claiming our shores may be a generation away, but what we do today will determine how well we can blunt that risk.

It’s against this backdrop that the 50-years-in-the-making flood protection plan proposed by the U.S. Army Corps of Engineers must be evaluated. The latest iteration of the infamous Fire Island to Montauk Point plan, known as FIMP, is budgeted tentatively at $1.2 billion, a total that has been growing. It was pegged at $750 million in 2013. It’s a lot of money; let’s make sure we get it right.

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The plan does have good elements, like its emphasis on re-establishing salt marshes to serve as natural defenses, while other aspects give us pause. But any debate over how to refine the granular details must be accompanied by an intense discussion of Long Island’s geographic future 30 and 50 and 80 years from now. That is not happening.

Here are some questions that must be addressed:

Does it make sense to invest in neighborhoods so flood-prone they might not outlive new roads and sewers?

Are there places where retreating would be wiser, where the best choice would be to return those properties to nature?

 

Should there be a regional coastal commission for LI and New York City with actual authority?

The plan proposes to elevate 6 miles of roads in Mastic Beach, Lindenhurst and Amityville that would act as quasi-dikes to shield 1,000 homes behind them. But that would do nothing for the Mastic Beach houses already besieged by groundwater flooding from a rising water table, homes whose lawns are wetlands vegetation, not grass. Can they be saved? And when a road deflects a storm surge, will the water harm someone else?

The plan calls for more pumping of sand from offshore sources onto beaches — never a permanent solution. That’s also at the heart of a $207 million emergency project to provide shorter-term protection for Fire Island communities that is about to enter its fourth and final phase. But in some parts of South Florida, which has been dredging since the 1970s, officials are running out of sand fit for beaches. Is Long Island’s offshore supply similarly finite?

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Undergirding the Corps’ plan is a projection that sea levels will rise at the rate of the past 100 years. But most models predict a faster rise as global warming worsens. The Corps projects an 8-inch rise by 2050; the midpoint of such estimates is twice that.

And the higher end, which anticipates no slowing of global warming, says the sea will rise 6 feet by 2100. That might seem a long way off, but many babies born this year will be alive then. And in the shorter term, other studies find a 50 percent chance that Long Island will experience at least one flood of more than 6 feet by 2050.

What would 6 feet of water do? An analysis of National Oceanic and Atmospheric Administration data by real estate data company Zillow Research says nearly 10 percent of homes in Nassau County would be underwater, along with 5.6 percent of homes in Suffolk, mostly on the low-lying South Shore.

Which estimate should we plan for?

Long Island is not the only region facing such dramatic changes or threats from storms like Hermine. The federal government is spending $48 million to move all 60 residents of Isle de Jean Charles, an island sinking into Louisiana’s coastal marsh. Last month, residents of a 600-person village on an Alaskan barrier island eaten away by storm surges voted to move to the mainland before their homes vanish; the estimated cost is at least $180 million. The 470 people on Virginia’s Tangier Island have about 50 years left before it is swallowed by the Chesapeake Bay.

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As these threats increase, limited federal dollars for protection are more likely to be spent on at-risk places like Miami and Manhattan.

 

The Army Corps will hold four public meetings this month on Long Island to explain the plan. To maximize feedback, it has extended the end of its comment period to Oct. 19. That’s good, as is its stated willingness to work with local communities on solutions.

This moment must be seized to have the conversation we must have. If it’s not, it will be another opportunity washed out with the tide.

Long Island is changing. Our thinking must change with it.