“That’s where we really need to clear out the structures,” said Mr. Behm, who retired in 2018. By contrast, he said the Corps’ current approach “scares a lot of community officials.”

The Corps defended its policy. Without using eminent domain, officials said, the Corps can’t guarantee to Congress that the buyouts lawmakers have funded will actually happen.

And that would leave residents still at risk. Imagine the Corps identifies 10 homes for buyouts, but only three people say yes, said Susan Layton, chief of planning and policy for the Corps’ Norfolk District office, which is working on buyout plans in Florida. With a voluntary program, that leaves seven homes still exposed. “You’re probably not doing your best job,” she said.

The Corps applies a relatively simple formula to decide which houses should be condemned, officials said: It estimates how much damage a house is likely to suffer in the next 50 years, then compares that to what it would cost to buy and tear down the house, plus moving expenses for the owner. If the buyout costs less, the homeowner is asked to sell for the assessed value of the home. That price is not negotiable, and neither is the offer.

Many officials have balked, at least for now. Miami-Dade has yet to agree to evict residents, and New Jersey has refused. In the Florida Keys, Roman Gastesi, the county administrator, said he doubted the county commission would approve it.

“Eminent domain is not something that’s going to be palatable,” Mr. Gastesi said, adding that the Corps should fund the buyout program it’s currently looking at in the Keys, but make it voluntary. “We don’t want to kick people out of their houses.”