The Federal Emergency Management Agency is refusing to retreat from new floodplain maps that D.C. officials fear could drastically affect future development across downtown Washington.

The new maps incorporate much of the city’s core into the 100-year floodplain, generally between Pennsylvania and Madison avenues and between Third Street Southwest and South Capitol Street. Most homeowners and businesses within the new plain will have to obtain flood insurance with annual premiums of at least $500, while developers will have to meet stringent and costly design standards.