Definitions of FEMA Flood Zone Designations
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 NFIP, flood insurance is available to all property owners and renters in these zones:
ZONE DESCRIPTION
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 shallow
flooding areas with average depths of less than one foot or drainage areas less
than 1 square mile.
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 DESCRIPTION
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.
AE – The base floodplain where base flood elevations are provided. AE Zones are now used
on new format FIRMs instead of A1‐A30 Zones.
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).
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.
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.
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.
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.
High Risk Coastal Areas
In communities that participate in the NFIP, mandatory flood insurance purchase requirements apply to all of these zones.
ZONE DESCRIPTION
V – Coastal areas with a 1% or greater chance of flooding and an additional hazard
associated with storm waves. These areas have a 26% chance of flooding over the life of
a 30‐year mortgage. No base flood elevations are shown within these zones.
VE, V1 ‐ 30 – Coastal areas with a 1% or greater chance of flooding and an additional hazard
associated with storm waves. 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.
Undetermined Risk Areas
ZONE DESCRIPTION
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.
