What is a Flood Insurance Rate Map (FIRM)?

A Flood Insurance Rate Map (FIRM) is an official map of a community on which

FEMA has delineated both the special hazard areas and the risk premium zones

applicable to the community.

What flood hazard zones are shown on the FIRM and

what do they mean?

Several areas of flood hazard are commonly identified on the DFIRM and

FIRM. One of these areas is the SFHA, which is defined as the area that would

be inundated by the flood event having a 1 percent chance of being equaled or

exceeded in any given year. The 1-percent-annual-chance flood is also referred

to as the “base flood.” SFHAs are labeled as Zone A, Zone AO, Zone AH, Zones

A1–A30, Zone AE, Zone 99, Zone AR, Zone AR/AE, Zone AR/AH, Zone AR/AO,

Zone AR/A1–A30, Zone AR/A, Zone V, Zone VE, and Zones V1–V30. Moderate

flood hazard areas, labeled Zone B, are also shown on the FIRM or DFIRM and are

the areas between the limits of the base flood and the 0.2-percent-annual-chance

flood. The areas of minimal flood hazard, which are the areas outside the SFHA

and higher than the elevation of the 0.2-percent-annual-chance flood, are labeled

Zone C. On new and revised maps, Zone X is used in place of Zones B and C. An

unshaded Zone X holds the same meaning as the labeled Zone B. A shaded Zone

X can mean any of the following: the area is in the 0.2 floodplain; is protected

by a levee; is subject to inundation by a flood event having a 1 percent chance of

reaching less than a 1.0-foot depth; is subject to inundation by a 1-percent-annualchance

flood within an area of less than 1 square mile; or is subject to inundation

by a 1-percent-annual-chance flood determined using future conditions. The

definitions for the various flood hazard areas are below.

Zone V: Primary frontal dunes and areas along coasts subject to inundation by

the 1-percent-annual-chance flood event with additional hazards associated with

storm-induced waves. Because detailed coastal analyses have not been performed,

no BFEs or flood depths are shown. Mandatory flood insurance purchase

requirements apply.

Zones VE and V1–V30: Primary frontal dunes and areas along coasts subject to

inundation by the 1-percent-annual-chance flood event with additional hazards

due to storm-induced velocity wave action. BFEs derived from detailed hydraulic

coastal analyses are shown within these zones. Mandatory flood insurance

purchase requirements apply. Zone VE is used on new and revised maps in place of

Zones V1–V30.

Zone A: Areas subject to inundation by the 1-percent-annual-chance flood event.

Because detailed hydraulic analyses have not been performed, no BFEs or flood

depths are shown. Mandatory flood insurance purchase requirements apply.

Zones AE and A1–A30: Areas subject to inundation by the 1-percent-annual-chance

flood event determined by detailed methods. BFEs are shown within these zones.

Mandatory flood insurance purchase requirements apply. (Zone AE is used on new

and revised maps in place of Zones A1–A30.)

Zone AH: Areas subject to inundation by 1-percent-annual-chance shallow flooding

(usually areas of ponding) where average depths are 1–3 feet. BFEs derived from

detailed hydraulic analyses are shown in this zone. Mandatory flood insurance

purchase requirements apply.

Zone AO: Areas subject to inundation by 1-percent-annual-chance shallow flooding

(usually sheet flow on sloping terrain) where average depths are 1–3 feet. Average

flood depths derived from detailed hydraulic analyses are shown within this zone.

Mandatory flood insurance purchase requirements apply.

Zone A99: Areas subject to inundation by the 1-percent-annual-chance flood event,

but which will ultimately be protected upon completion of an under-construction

Federal flood protection system. These are areas of special flood hazard where

enough progress has been made on the construction of a protection system, such

as dikes, dams, and levees, to consider it complete for insurance rating purposes.

Zone A99 may be used only when the flood protection system has reached

specified statutory progress toward completion. No BFEs or flood depths are

shown. Mandatory flood insurance purchase requirements apply.

Zone AR: Areas that result from the decertification of a previously accredited

flood protection system that is determined to be in the process of being

restored to provide base flood protection. Mandatory flood insurance purchase

requirements apply.

Zones AR/AE, AR/AH, AR/AO, AR/A1–A30, and AR/A: Dual flood zones that,

because of the risk of flooding from other water sources that the flood protection

system does not contain, will continue to be subject to flooding after the flood

protection system is adequately restored. Mandatory flood insurance purchase

requirements apply.

Zones B, C, and X: Areas identified in a community’s FIS as areas of moderate or

minimal hazard from the principal source of flood in the area. However, buildings

in these zones could be flooded by severe, concentrated rainfall coupled with

inadequate local drainage systems. Local stormwater drainage systems are not

normally considered in a community’s FIS. The failure of a local drainage system

creates areas of high flood risk within these rate zones. Flood insurance is available

in participating communities but is not required by regulation in these zones.

Zone X is used on new and revised maps in place of Zones B and C.

Zone D: Unstudied areas where flood hazards are undetermined, but flooding

is possible. No mandatory flood insurance purchase requirements apply, but

coverage is available in participating communities.