Flood zones are geographic areas that the FEMA has defined according to varying levels of flood risk. These zones are depicted on a community’s Flood Insurance Rate Map (FIRM) or Flood Hazard Boundary Map. Each zone reflects the severity or type of flooding in the area.
Moderate to Low Risk Areas
In communities that participate in the National Flood Insurance Program (NFIP), flood insurance is available to all property owners and renters in these zones:
Zones B and X (shaded)
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 100‐year flood, or shallowflooding areas with average depths of less than one foot or drainage areas lessthan 1 square mile.
Zones C and 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 100‐ year flood.
High Risk Areas
In communities that participate in the NFIP, mandatory flood insurance purchase requirements apply to all of these zones:
Zone A Areas with a 1% annual chance of flooding and a 26% chance of flooding over the life of a 30‐year mortgage. Because detailed analyses are not performed for such areas; no depths or base flood elevations are shown within these zones. Zone AE The base floodplain where base flood elevations are provided.
AE Zones are now used on new format FIRMs instead of A1‐A30 Zones.
Zone A1‐30 These are known as numbered A Zones (e.g., A7 or A14). This is the base floodplain where the FIRM shows a BFE (old format).
Zone AH Areas with a 1% annual chance of shallow flooding, usually in the form of a pond, with an average depth ranging from 1 to 3 feet. These areas have a 26% chance of flooding over the life of a 30‐year mortgage. Base flood elevations derived from detailed analyses are shown at selected intervals within these zones.
Zone AO River or stream flood hazard areas, and areas with a 1% or greater chance of shallow flooding each year, usually in the form of sheet flow, with an average depth ranging from 1 to 3 feet. These areas have a 26% chance of flooding over the life of a 30‐year mortgage. Average flood depths derived from detailed analyses are shown within these zones.
Zone AR Areas with a temporarily increased flood risk due to the building or restoration of a flood control system (such as a levee or a dam). Mandatory flood insurance purchase requirements will apply, but rates will not exceed the rates for unnumbered A zones if the structure is built or restored in compliance with Zone AR floodplain management regulations.
Zone A99 Areas with a 1% annual chance of flooding that will be protected by a Federal flood control system where construction has reached specified legal requirements. No depths or base flood elevations are shown within these zones.
Undetermined Risk Areas
Zone D Areas with possible but undetermined flood hazards. No flood hazard analysis has been conducted. Flood insurance rates are commensurate with the uncertainty of the flood risk.