What are flood hazard zones and what do they mean?

WHAT ARE FLOOD HAZARD ZONES AND WHAT DO THEY MEAN?

The Flood Insurance Rate Map (FIRM) is used in regular program communities by lenders to determine the
flood insurance requirements and by insurance agents to determine flood insurance premium rates for
specific properties. The map includes areas within the 100-year flood boundary, which are termed "Special
Flood Hazard Areas" (SFHAs). A "100-year flood" does not refer to a flood that occurs once every 100
years, but refers to a flood level with a 1 percent or greater chance of being equaled or exceeded in any
given year.

The SFHAs may be further subdivided into insurance risk rate zones. Areas between the 100-year and
500-year flood boundaries are termed "moderate flood hazard areas". The remaining areas are above the
500-year flood level and are termed "minimal flood hazard areas".

Historically, about one-third of claims paid by the NFIP are for flood damage in areas identified as having
only "moderate" and "minimal" risk of flood. Flooding in these areas often is the result of inadequate local
drainage systems, and such flooding sources with small drainage areas are generally not identified on
FIRMs.

The SFHAs are subdivided into flood hazard zones (insurance risk rate zones) according to the following
criteria:

Zone A is the flood insurance rate zone that corresponds to the 1-percent annual chance floodplains that
are determined in the Flood Insurance Study by approximate methods of analysis. Because detailed
hydraulic analyses are not performed for such areas, no Base Flood Elevations or depths are shown within
this zone. Mandatory flood insurance purchase requirements apply.

Zones AE and A1-A30 are the flood insurance rate zones that correspond to the 1-percent annual chance
floodplains that are determined in the Flood Insurance Study by detailed methods of analysis. In most
instances, Base Flood Elevations derived from the detailed hydraulic analyses are shown at selected
intervals within this zone. Mandatory flood insurance purchase requirements apply.

Zone AH is the flood insurance rate zone that corresponds to the areas of 1-percent annual chance
shallow flooding with a constant water-surface elevation (usually areas of ponding) where average depths
are between 1 and 3 feet. The Base Flood Elevations derived from the detailed hydraulic analyses are
shown at selected intervals within this zone. Mandatory flood insurance purchase requirements apply.

Zone AO is the flood insurance rate zone that corresponds to the areas of 1-percent shallow flooding
(usually sheet flow on sloping terrain) where average depths are between 1 and 3 feet. Average flood
depths derived from the detailed hydraulic analyses are shown within this zone. In addition, alluvial fan
flood hazards are shown as Zone AO on the Flood Insurance Rate Map. Mandatory flood insurance
purchase requirements apply.

Zone AR is the flood insurance rate zone used to depict areas protected from flood hazards by flood
control structures, such as a levee, that are being restored. FEMA will consider using the Zone AR
designation for a community if the flood protection system has been deemed restorable by a Federal
agency in consultation with a local project sponsor; a minimum level of flood protection is still provided to
the community by the system; and restoration of the flood protection system is scheduled to begin within a
designated time period and in accordance with a progress plan negotiated between the community and
FEMA. Mandatory purchase requirements for flood insurance will apply in Zone AR, but the rate will not
exceed the rate for an unnumbered Zone A if the structure is built in compliance with Zone AR floodplain
management regulations.

For floodplain management in Zone AR areas, the property owner is not required to elevate an existing
structure when making improvements to the structure. However, for new construction, the structure must be
elevated (or floodproofed for non-residential structures) so that the lowest floor, including basement, is a
minimum of 3 feet above the highest adjacent existing grade, if the depth of the Base Flood Elevation
(BFE) does not exceed 5 feet at the proposed development site. For infill sites, rehabilitation of existing
structures, or redevelopment of previously developed areas, there is a 3-foot elevation requirement
regardless of the depth of the BFE at the project site.

The Zone AR designation will be removed and the restored flood control system will be shown as providing
protection from the 1-percent annual chance flood on the National Flood Insurance Program map upon
completion of the restoration project and submittal of all the necessary data to FEMA.

Zone A99 is the flood insurance rate zone that corresponds to areas within the 1-percent annual chance
floodplain that will be protected by a Federal flood protection system where construction has reached
specified statutory milestones. No Base Flood Elevations or depths are shown within this zone. Mandatory
flood insurance purchase requirements apply.

Zone D designation is used for areas where there are possible but undetermined flood hazards. In areas
designated as Zone D, no analysis of flood hazards has been conducted. Mandatory flood insurance
purchase requirements do not apply, but coverage is available. The flood insurance rates for properties in
Zone D are commensurate with the uncertainty of the flood risk.

Zone V is the flood insurance rate zone that corresponds to areas within the 1-percent annual chance
coastal floodplains that have additional hazards associated with storm waves. Because approximate
hydraulic analyses are performed for such areas, no Base Flood Elevations are shown within this zone.
Mandatory flood insurance purchase requirements apply.

Zone VE is the flood insurance rate zone that corresponds to areas within the 1-percent annual chance
coastal floodplain that have additional hazards associated with storm waves. Base Flood Elevations
derived from the detailed hydraulic analyses are shown at selected intervals within this zone. Mandatory
flood insurance purchase requirements apply.

Zones B, C, and X are the flood insurance rate zones that correspond to areas outside the 1-percent
annual chance floodplain, areas of 1-percent annual chance sheet flow flooding where average depths are
less than 1 foot, areas of 1-percent annual chance stream flooding where the contributing drainage area is
less than 1 square mile, or areas protected from the 1-percent annual chance flood by levees. No Base
Flood Elevations or depths are shown within this zone. Insurance purchase is not required in these zones.