Floods happen more than you’d think. In fact, almost 90% of all natural disasters involve flooding. To reflect the risks in each part of the country, the Federal Emergency Management Agency (FEMA) has issued Flood Insurance Rate Maps (FIRMs) that show areas of high and moderate to low risk of flooding. More than 20,000 cities fall into a category of flood zones, which is determined by a letter and/or number.
Flood Zone Classification
A zones are subject to rising waters and are usually near a lake, river, stream or another body of water. Flood insurance is compulsory in all A zones because of the high potential of flooding.
- A Zone: These are areas with a 1% annual probability of flooding and a 26% chance of flooding over a 30‐year mortgage. As there are no detailed analyses for such areas, no depths or base flood elevations are shown.
- AE and A1‐30 Zones: These zones are subject to a 1% annual chance of flooding. Base Flood Elevations (BFEs) are shown.
- AH Zone: These zones have a 1% annual possibility of shallow flooding, generally in the form of a pond, with an average depth ranging from 1 to 3 feet. They have a 26% chance of flooding over the life of a 30‐year mortgage.
- AO Zone: These zones include river/stream flood hazard areas and areas with a 1% or greater chance of shallow flooding each year, normally in the form of sheet flow, with an average depth varying from 1 to 3 feet. These zones have a 26% chance of flooding over the life of a 30‐year mortgage.
- AR Zone: Areas with a temporarily increased flood risk due to the building or restoration of a flood control system. Obligatory flood insurance purchase requirements apply, but rates will not surpass the rates for unnumbered A zones if the structure is built or restored complying with Zone AR floodplain management regulations.
- A99 Zone: These are areas with a 1% annual possibility of flooding that will be protected by a Federal flood control system. No depths or base flood elevations are shown in these areas.
According to FEMA, V zones, which include first-row beachfront properties, are the most hazardous of the Special Flood Hazard Areas. Flood insurance is compulsory in V zone areas.
- V Zone: These zones include coastal areas with a 1% or greater chance of flooding and an additional hazard associated with storm waves. They 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 Zone: These areas differ from the V zones as they require base flood elevations derived from detailed analyses.
- B and X Zone: These are areas of moderate flood hazard, generally the area between the limits of the 100‐ year and 500‐year floods. B Zones are also used to establish base floodplains of lesser hazards or shallow flooding areas with average depths of less than 1 foot or drainage areas less than 1 square mile.
- C and X Zone: These zones include areas of minimal flood hazard, usually described on FIRMs as above the 500‐year flood level. Zone C may have ponding and local drainage problems that don’t need a detailed study or designation as base floodplain. Zone X is the area defined to be outside the 500‐year flood and protected by levee from 100‐ year flood.
- D Zone: These zones include areas with possible but undetermined flood hazards. No flood hazard analysis has been carried out. Flood insurance rates are commensurated with the uncertainty of the flood risk.
If you are interested in understanding more about your zone, please refer to the FEMA Map Service Center. Flood maps are also kept on file at your local library, county courthouse or municipal office.