FEMA Flood Zones

How to Interpret the FEMA FIRM Rate Maps

Whatever the area shown on a FEMA FIRM map, it may include several types of floodplain zones, each designated by a letter or a combination of a letter and number(s). Please see the table below for explanations of these zones.

Zone Explanations

ZoneThe 100-year or base floodplain. Six types of 'A' zones are described below.
ABase flood elevations (BFE) are not determined. This is often called an unnumbered A Zone or an approximate A zone.
A1-30Known as numbered A Zones (e.g., A7 or A14). BFEs are shown on a FEMA map that includes any of these zones.
AEOn newer FIRMs, AE Zones are the same as A1-A30 Zones (i.e., BFEs are shown).
AOThe base floodplain with sheet flow, ponding or shallow flooding. Base flood depths (feet above ground) are provided.
AHShallow-flooding base floodplain. BFEs are provided.
A99Area to be protected from base flood by levees or Federal Flood Protection Systems under construction. BFEs are not determined.
ARThe base floodplain that results from the decertification of a previously accredited flood protection system that is in the process of being restored to provide a 100-year or greater level of flood protection.
Zone VThe coastal area subject to a velocity hazard (wave action) where BFEs are not determined on the FIRM map.
Zone VEThe coastal area subject to a velocity hazard (wave action) where BFEs are provided on the FIRM map.
Zone B and Zone X Area of moderate flood hazard, usually the area between the limits of the 100-year and 500-year floods. B Zones are also used to designate base floodplains of lesser hazards, such as areas protected by levees from the 100-year flood, or shallow-flooding areas with average depths of less than one foot or drainage areas less than 1 square mile.
Zone C and Zone X (unshaded)Area of minimal flood hazard, usually depicted on FIRMs as above the 500-year flood level. Zone C may have ponding and local drainage problems that don't warrant a detailed study or designation as base floodplain. Zone X is the area determined to be outside the 500-year flood and protected by levee from the 100-year flood.
Zone DArea of undetermined but possible flood hazards.