What is a Flood Zone?
Federal Emergency Management Agency (FEMA) maintains and updates flood maps that identify the risk of flooding in a community by assigning flood zone categories to different parts of the map. Flood maps are also known as Flood Insurance Rate Map (FIRM).
Within a flood map, a flood zone denotes the level of risk for flooding in a particular area. Flood zones are assigned codes that denote different levels of risk. The flood zone codes used are A, AO, AH, A1-A30, AE, A99, AR, AR/A, AR/AE, AR/AO, AR/A1-A30, AR/A, V, VE, V1-V30, B, C, X, D.
Special Flood Hazard Area (SFHA) - High Risk Areas
Special Flood Hazard Area (SFHA) is defined as the area that will 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 or 100-year flood. In the context of mortgages, there is at least a 1 in 4 chance of flooding during a 30-year mortgage. All flood zones beginning with the letter "A" or "V" are considered SFHAs. If any part of the building or mobile home is within the SFHA, the entire building or mobile home is considered to be in the SFHA.
Base Flood Elevation (BFE) refers to the computed elevation to which floodwater is anticipated to rise during the base flood. The land area covered by the floodwaters of the base flood is the base floodplain. On NFIP maps, the base floodplain is called the Special Flood Hazard Area (SFHA).
The base floodplain mapped by approximate methods, i.e., BFEs are not determined. This is often called an unnumbered A Zone or an approximate A Zone.
These are known as numbered A Zones (e.g., A7 or A14). This is the base floodplain where the FIRM shows a BFE (old format).
The base floodplain where base flood elevations are provided. AE Zones are now used on new format FIRMs instead of A1-A30 Zones.
The base floodplain with sheet flow, ponding, or shallow flooding. Base flood depths (feet above ground) are provided.
Shallow flooding base floodplain. BFEs are provided.
Area to be protected from base flood by levees or Federal Flood Protection Systems under construction. BFEs are not determined.
The base floodplain that results from the decertification of a previously accredited flood protection system that is in the process of being restored to provide a 100-year or greater level of flood protection.
Zone V and VE
The coastal area subject to a velocity hazard (wave action) where BFEs are not determined on the FIRM.
The coastal area subject to a velocity hazard (wave action) where BFEs are provided on the FIRM.
Non Special Flood Hazard Area (NSFAs) - Moderate-to-Low Risk Areas
Zone B and Zone X (shaded)
B and X (shaded)
Area of moderate flood hazard, usually the area between the limits of the 100-year and 500-year floods. B Zones are also used to designate base floodplains of lesser hazards, such as areas protected by levees from the 100-year flood, or shallow flooding areas with average depths of less than one foot or drainage areas less than 1 square mile.
Zone C and Zone X (unshaded)
C and X (unshaded)
Area of minimal flood hazard, usually depicted on FIRMs as above the 500-year flood level. Zone C may have ponding and local drainage problems that don’t warrant a detailed study or designation as base floodplain. Zone X is the area determined to be outside the 500-year flood and protected by levee from 100-year flood.
Undetermined Risk Areas
Flood-hazard analysis has not been conducted in these areas. Flood risk still exists, but has not been identified.
Area of undetermined but possible flood hazards.