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Flood Zones and Terms

Definitions of Flood Zones and related terms are provided below.

Information regarding flood recurrence intervals and the relationship to storm events can be found at the United States Geological Survey (USGS) website.

Base Flood: The flood having a 1% chance of being equaled or exceeded in any given year, also known as the "100-year" or "1% chance" flood. The base flood is a statistical concept used to ensure that all properties subject to the National Flood Insurance Program are protected to the same degree against flooding.

BFE (Base Flood Elevation): The expected elevation the base flood will reach. 

FIRM (Flood Insurance Rate Map): The flood hazard map provided by the Federal Emergency Management Agency (FEMA) and adopted by our community. The current effective date of our FIRM is March 14, 2013. 

FIS (Flood Insurance Study): The study provided by FEMA that graphically represents flood heights for certain areas of the floodplain.

SFHA (Special Flood Hazard Area): The base floodplain delineated on a Flood Insurance Rate Map. The SFHA is mapped as Zone A. The SFHA may not encompass all of the City of Austell’s flood problems.

Zone A: The SFHA shown on a community’s FIRM. The types of A Zones that may be applicable to the City of Austell:

  • A: SFHA where no base flood elevation is provided.
  • AE: SFHA where the base flood elevations are provided.
  • AO: SFHA with sheet flow, ponding, or shallow flooding. Base flood depths (feet above grade) are provided.

‘Shaded’ Zone X: Area of moderate flood hazard usually depicted on FIRMs as between the limits of the base and 500-year floods of the primary source of flooding. 

Flood Hazard Information Assistance

Austell Public Works Stormwater Management provides Flood Insurance Rate Map determinations to let you know if you are in a flood hazard area. Approximate maps of the regulated floodplain are available on the Georgia DFIRM flood map viewer website. You may also create and print a FIRMette at the FEMA Map Service Center website. For additional information, you may contact the Austell Public Works Stormwater Management division at (770) 944-4325 or by e-mail to

Related Links

Georgia Department of Natural Resources Flood Map Viewer

FEMA Map Service Center