Floodplan Term Definitions
The following information gives an explanation for the flood zone designations used by First American Flood Data Services:
Zone V: An area inundated by 100-year flooding with velocity hazard (wave action); no BFEs have been determined.
Zone VE: An area inundated by 100-year flooding with velocity hazard (wave action); BFEs have been determined.
Zone A: An area inundated by 100-year flooding, for which no BFEs have been determined.
Zone AE: An area inundated by 100-year flooding, for which BFEs have been determined.
Zone AO: An area inundated by 100-year flooding (usually sheet flow on sloping terrain), for which average depths have been determined; flood depths range from 1 to 3 feet.
Zone AO (Alluvial Fan): An alluvial fan inundated by 100-year flooding (usually sheet flow on sloping terrain), for which average flood depths and velocities have been determined; flood depths range from 1 to 3 feet.
Zone AH: An area inundated by 100-year flooding (usually an area of ponding), for which BFEs have been determined; flood depths range from 1 to 3 feet.
Zone A99: An area inundated by 100-year flooding, for which no BFEs have been determined. This is an area to be protected from the 100-year flood by a Federal flood protection system under construction.
Zone D: An area of undetermined but possible flood hazards.
Zone AR: An area inundated by flooding, for which BFEs or average depths have been determined. This is an area that was previously, and will again, be protected from the 100-year flood by a Federal flood protection system whose restoration is Federally funded and underway.
Zone X: An area inundated by 500-year flooding; an area inundated by 100-year flooding with average depths of less than 1 foot or with drainage areas less than 1 square mile; or an area protected by levees from 100-year flooding.
Zone XX: An area that is determined to be outside the 100- and 500-year floodplains.