Unbowed, he continues to preach against incremental measures. "If you get a storm and a big oak tree falls on your house, then whether you fix your gutter doesn't matter," he said.
In recent years, his logic has finally begun to resonate a bit more. Nicholas Kim, an oceanographer with engineering firm HDR HydroQual who studied with Bowman in the 1980s, said his mentor has been thinking about barriers since then: "Everybody said, 'You're crazy!' But now it's becoming clear that we need protection."
Even massive structures don't shield everyone, though. A 2009 four-barrier study co-authored by Kim found that in a simulated storm, barriers still failed to protect large swaths of Queens and sections of other outlying boroughs with a total of more than 100,000 people.
Researchers also have predicted at least a modest additional one-foot rise of stormy seas as water piles up outside the barriers. "If you're the guy just outside the barrier, and you're paying taxes and you're not included, you're not going to be very happy," said oceanographer Larry Swanson at Stony Brook University.
How such barriers would affect water movement, silt and marine life also remains an open question requiring further study for each case.
The scale and costs of hard barrier schemes have further put off many critics. After flooding from Hurricane Irene last year, city representatives asked Aerts, the Dutch planner, to compare the cost and benefits of barriers to existing approaches. His initial analysis will not be finished until February, but his early cost estimate for barriers and associated dikes for New York City is $15 billion to $27 billion — comparable to that of the record-setting $24 billion Big Dig that reshaped Boston's waterfront — not to block storms, but to unblock traffic and views of the waterfront.
Barrier defenders counter by pointing to the cost of storm damages. Stony Brook meteorologist Brian Colle said: "When you think of the cost of a Sandy, which is running in the billions, these barriers are basically going to pay for themselves in one or two storms." Advocates say tolls on trains or cars riding atop a barrier could help finance the project.
While appealing for rebuilding, Council Speaker Quinn also has said that "the time for casual debate is over" and called for a bold mix of resiliency with grander protective structures. She has estimated the cost of her plan at $20 billion.
Other massive protection schemes, like the green makeover of lower Manhattan, also would probably run into the billions. And soft protections are meant only to defuse, not stop, rising waters. Sandy battered parts of Long Island behind barrier islands and wetlands.
Nor is it clear that Manhattan has enough space to fashion more extensive wetlands of the sort that help protect the Gulf Coast, however imperfectly. "New York is too far gone for wetlands," said Griffis, the retired Army Corps commander for New York.
Sen. Charles Schumer, D-N.Y., has announced he will spearhead efforts to request a corps study of whether barriers or other options would work better. However, it remains unclear if Congress would be willing to fund such a study, which would undoubtedly take several years and cost millions of dollars.
And even before a dime has been appropriated, the corps is lowering expectations. Says spokesman Chris Gardner: "You can't protect everywhere completely at all times."
Associated Press National Writer Adam Geller and AP researcher Julie Reed contributed to this report.
The AP National Investigative Team can be reached at investigate(at)ap.org