Still, many residents of Isle de Jean Charles do not want to leave. Attachment to the island runs deep. Parents and grandparents lived here; there is a cemetery on the island that no one wants to abandon. Old and well-earned distrust of the government hangs over all efforts, and a bitter dispute between the two Indian tribes with members on the island has thwarted efforts to unite behind a plan.

“Ain’t nobody I talk to that wants to move,” said Edison Dardar, 66, a lifelong resident who has erected handwritten signs at the entrance to the island declaring his refusal to leave. “I don’t know who’s in charge of all this.”

Whether to leave is only the first of the hard questions: Where does everyone go? What claim do they have to what is left behind? Will they be welcomed by their new neighbors? Will there be work nearby? Who will be allowed to join them?

“This is not just a simple matter of writing a check and moving happily to a place where they are embraced by their new neighbors,” said Mark Davis, the director of the Tulane Institute on Water Resources Law and Policy.

“If you have a hard time moving dozens of people,” he continued, “it becomes impossible in any kind of organized or fair way to move thousands, or hundreds of thousands, or, if you look at the forecast for South Florida, maybe even millions.”