What are the Flood Zones?
There are six (6) flood zone designations. Some zones have multiple sub-designations, as follows:
- Zone "A" (and its sub-designations: AE, AH, AO and A1-A99). The 100 year or base floodplain.
There are six types of A Zones.
- A: The base flood mapped by approximate method, i.e., base flood elevations is not provided. This is often called an unnumbered A Zone or an approximate A Zone.
- A1-A30: These are known as numbered A Zones (e.g., A7 or A14). This is the base floodplain where the FIRM shows a base flood elevation (old format).
- AE: The base floodplain where base flood elevations are provided. AE Zone delineations are now used on new format FIRMs instead of A1-A30 Zones.
- AO: The base floodplain with sheet flow, ponding or shallow flooding. Base flood depths (feet above ground) are provided.
- AH: Shallow flooding base floodplain. Base flood elevations are provided.
- AR: 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.
All lenders must require borrowers to purchase and maintain flood insurance for Zone "A" properties.
- Zone “V” – The base floodplain subject to coastal high hazard flooding. There are three types of V Zones: V, V1-30 and VE that correspond to the similar A Zone designations. There are no V Zones in Illinois.
- Zone B and Zone X (shaded) – Area of moderate flood hazard, usually the area between the limits of the 100-year and 500-year floods. It can also be an area of the base flood (1) with average depths of less than one foot, (2)with a drainage area less than one square mile or (3) protected by levees from the base flood.
- Zone C and Zone X (unshaded) - Area of minimal flood hazard, usually depicted on FIRMs as above the 500-year flood level. B and C Zones may have ponding and local drainage problems that don’t warrant a detailed study or designation as base floodplain.
- Zone D- Area of undetermined but possible flood hazard.