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Zone A
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Zone A is the flood insurance risk zone that corresponds to the 1-percent-annual-chance floodplains that are determined in the FIS by approximate methods. Because detailed hydraulic analyses are not performed for such areas, no base flood elevations or depths are shown within this zone.
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Zone AE
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Zone AE is the flood insurance risk zone that corresponds to the 1-percent-annual-chance flood plains that are determined in the FIS by detailed methods. In most instances, base flood elevations derived from the detailed hydraulic analyses are shown at selected intervals within this zone.
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Zone AH
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Zone AH is the flood insurance risk 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.
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Zone AO
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Zone AO is the flood insurance risk zone that corresponds to the 1-percent-annual-chance shallow flooding (usually sheet flow on sloping terrain) where average depths are between 1 and 3 feet. The depth should be averaged along the cross section and then along the direction of flow to determine the extent of the zone. Average 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 FIRM.
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Zone A99
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Zone A99 is the flood insurance risk zone that corresponds to 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.
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Zone AR
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Zone AR is the flood insurance risk zone that corresponds to areas of special flood hazard that results from the decertification of a previously accredited flood protection system that is determined to be in the process of being restored to provide a 1-percent-annual-chance or greater level of flood protection.
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Zone AR/A; AR/AE; AR/AO; and AR/AH
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Zone AR/A, AR/AE, AR/AO, and AR/AH are dual flood insurance risk zones that correspond to areas of special flood hazard 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 a 1-percent-annual-chance or greater level of flood protection. The dual-zone designation indicates that some residual 1-percent-annual-chance flooding will occur after the levee system has been restored and is credited with providing 1-percent-annual-chance flood protection.
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Zone V
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Zone V is the flood insurance risk zone that corresponds to 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.
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Zone VE
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Zone VE is the flood insurance risk zone that corresponds to the 1-percent-annual-chance coastal floodplains 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.
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Zone X
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Zone X is the flood insurance risk zone that corresponds to areas outside the 1-percent-annual-chance floodplain, and 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.
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Zone D
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Zone D is the flood insurance risk zone that corresponds to unstudied areas where flood hazards are undetermined, but possible. Zone D designation may not be used in Flood Insurance Studies unless otherwise approved by the Regional Project Officer. It should be noted that the Mapping Partner is not required to perform a flood hazard factor analysis and subsequent Zone A1-A30 or AE determination even though this information may currently be reflected on a community's FIRM published in the non-map initiative format.
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