The COE doesn't have to buy out any land, pay to move people or rebuild any city. When these morons living on the flood plains get flooded out every year or so, either their flood insurance or FEMA pays for their damages. That money could be better spent on buying a new home where they wouldn't need to be bailed out year after year.
Give them a warning. They get paid once, and then they're on their own. And any new homes built on the flood plains, after a certain date, get no FEMA flood protection at all. It's that simple.