“The idea is that you raise these barriers, and anywhere inside of that you’re basically protected,” Dr. Colle said, adding, “With a solid barrier, we basically can have business as usual in Lower Manhattan.”

But vexing questions remain. Would industries tolerate immense disruption from the construction of barriers in the city’s busy waterways? Would residents object to the marring of vistas? With climate change advancing, can scientists accurately predict the size of hurricanes that the sea gates would one day have to withstand?

And where would the $10 billion-plus in construction money come from? Even a study — taking into account the complexity of New York waterways, projections in the rise in sea levels and other factors — would take years and millions of dollars.

The scientists and engineers who have worked on conceptual designs for the city say a comprehensive study is needed on what would be the most effective locations and the most practical type of barriers — whether they swing close like a driveway gate or pivot up from the ocean floor, for example.

A feasibility study by the Army Corps of Engineers, which would have jurisdiction, would require authorization from Congress.

“A lot of things need to be taken into consideration before we throw up a giant wall,” said Chris Gardner, a spokesman for the corps.

Beyond the enormous potential cost, there is no question that there are drawbacks to sea barriers. A barrier that blocks the surge on one side would cause water levels on the other to rise close to a foot, Dr. Colle said, potentially worsening flooding in other areas.