FEMA Flood Zone Definitions

 

Touchstone hazard analyses use both DFIRM (Digital Flood Insurance Rate Map) and Q3FIRM (Q3 Flood Insurance Rate Map)  zones. The digital Q3 Flood Data product was the first flood map product that FEMA produced; FEMA now only updates or produces DFIRMs. DFIRMs are comprised of all digital data required to create the hardcopy FIRM, including base map information, graphics, text, shading, and other geographic data.

DFIRM Zones

Zone/Color

Definition

500IC

An area where the 500-year flooding is contained within the channel banks and the channel is too narrow to show to scale. An arbitrary channel width of 3 meters is shown. An area inundated by 100-year flooding, for which no Base Flood Elevations have been determined.

A99

An area inundated by 100-year flooding, for which no Base Flood Elevations have been determined. This is an area to be protected from the 100-year flood by a Federal flood protection system under construction.

A

An area inundated by 100-year flooding, for which no Base Flood Elevations have been determined.

AE

An area inundated by 100-year flooding, for which Base Flood Elevations have been determined.

AH

An area inundated by 100-year flooding (usually an area of ponding), for which Base Flood Elevations have been determined; flood depths range from 1 to 3 feet.

AO

An area inundated by 100-year flooding (usually sheet flow on sloping terrain), for which average depths have been determined; flood depths range from 1 to 3 feet.

D

An area of undetermined but possible flood hazards.

FWIC

An area where the floodway is contained within the channel banks and the channel is too narrow to show to scale. An arbitrary channel width of 3 meters is shown. Base Flood Elevations are not shown in this area, although they may be reflected on the corresponding profile.

UNDES

A body of open water, such as a pond, lake ocean, etc., located within a community's jurisdictional limits, that has no defined flood hazard.

V

An area inundated by 100-year flooding with velocity hazard (wave action); no Base Flood Elevations have been determined.

VE

An area inundated by 100-year flooding with velocity hazard (wave action); Base Flood Elevations have been determined.

X500

An area inundated by 500-year flooding; an area inundated by 100-year flooding with average depths of less than 1 foot or with drainage areas less than 1 square mile; or an area protected by levees from 100-year flooding.

X

Zone X is a low-risk area that is outside the 100- and 500-year floodplains, or is protected by levees. This zone has a 1% annual chance of sheet flow flooding where average depths are less than one foot, and 1% annual chance of stream flooding where the drainage area is less than 1 square mile. There are no base flood elevations or depths in this zone.

Q3FIRM Zones

100IC

An area where the 100-year flooding is contained  within the channel banks and the channel is too narrow to show to scale. An arbitrary channel width of 3 meters is shown. Base Flood Elevations are not shown in this area, although they may be reflected on the corresponding profile.

ANI

An area that is located within a community or county that is not mapped on any published Flood Insurance Rate Map (FIRM).

AOVEL

An alluvial fan inundated by 100-year flooding (usually sheet flow on sloping terrain), for which average flood depths and velocities have been determined; flood depths range from 1 to 3 feet.

AR

An area inundated by flooding, for which Base Flood Elevations or average depths have been determined. This is an area that was previously, and will again, be protected from the 100-year flood by a Federal flood protection system whose restoration is Federally funded and underway.

B, C

Zones B are C are low-risk areas that are outside the 100- and 500-year floodplains, or are protected by levees. These zones have a 1% annual chance of sheet flow flooding where average depths are less than one foot, and 1% annual chance of stream flooding where the drainage area is less than 1 square mile. There are no base flood elevations or depths in these zones.

FPQ

An area designated as a "Flood Prone Area" on a map prepared by USGS and the Federal Insurance Administration. This area has been delineated based on available information on past floods. This is an area inundated by 100-year flooding for which no Base Flood Elevations have been determined.

IN

An area designated as within a "Special Flood Hazard Area" (SFHA) on a FIRM. This is an area inundated by 100-year flooding for which Base Flood Elevations or velocity may have been determined. No distinctions are made between the different flood hazard zones that may be included within the SFHA. These may include zones A, AE, AO, AH, A99, AR, V, or VE.

OUT

An area designated as outside a "Special Flood Hazard Area" (SFHA) on a FIRM. This is an area inundated by 500-year flooding; an area inundated by 100-year flooding with average depths of less than 1 foot or with drainage areas less than 1 square mile; an area protected by levees from 100-year flooding; or an area that is determined to be outside the 100- and 500-year floodplains. No distinctions are made between these different conditions. These may include both shaded and unshaded areas of Zone X.

 

 

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Touchstone V3.0 Updated December 01, 2016