“If we’re going to have redundant systems”— backup generators, for instance — “it’s obviously going to be better not to have them in the basement.” Various kinds of machinery will need to be relocated to the tops of buildings. “That’s the most basic, fundamental thing,” he said.

Image Water threatened Jane’s Carousel in Brooklyn Bridge Park on Monday. Credit... Brian Morrissey/Associated Press

And yet the anxiety of New Yorkers is powerful, and so it doesn’t seem preposterous to speculate that no matter what sort of precautions are taken, certain people will forgo the romance of the waterfront in favor of higher ground. It was part of the great tragedy of Hurricane Katrina that the poor seemed to suffer worst, while the better off, living farther above sea level, fared much better. Historically, in many cities of course, elevation has held cachet.

It’s the needy who have been sequestered downward. Not long ago, Ms. Drake, a landscape architect, curious about the placement of New York City’s public housing, devised a map to find out how much of it was built on flood zones. The answer, she discovered, was, most of it. Public housing lines the waterfront in Coney Island, on the Lower East Side, in the Rockaways. This is not the result of progressive and munificent city planning aimed at enhancing the day-to-day aesthetic experience of the poor. Instead it was the result of low-lying waterfront land available at a cheap price. In her book “Manhattan: Water Bound,” the urban planner Ann L. Buttenwieser explains that land on which the Vladeck Houses on Water Street were built in 1939 was bought for $7 a square foot.

Eight years earlier, in 1931, when the River House, which would become one of the most exclusive residences in New York, went up on the far end of East 52nd Street, it took a kind of distinctly unconventional elitism to live there. The building replaced a cigar factory and furniture plant. Below, in the 40s on the East River, were slaughterhouses and the attendant brothels and beer halls. Then — as now, in some cases — the commitment to living on the waterfront would have had to arrive with a sort of fetishizing, realized or sublimated, of working-class life.

But then, unlike in the present day, the water offered something practical beyond a view. It offered a boat landing (from which the department store heir Marshall Field III could get to his house on Long Island in 35 minutes). Your investment delivered an unsurpassable fantasy: escape.