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 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 FEMA and adopted by our community. The current effective date of our FIRM is 06/02/99.

FIS (FIood 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 community’s flood problems.
Zone A: The SFHA shown on a community’s FIRM. The types of A Zones that are applicable to our community:
  • 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.

Zone X: Newer FIRMs show Zones B and C as Zone X. The shaded Zone X corresponds to Zone B and the unshaded Zone X corresponds to Zone C.
‘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. B Zones may have local, shallow flooding problems.
Flood Hazard Information Assistance
The City of Eugene provides free information regarding the flood hazard for specific sites within our community and related issues at the Permit & Information Center. We can be reached by phone at 682-8400 or in person at 99 W. 10th Avenue. We are open to the public from 9 AM to 5 PM Monday through Friday. We strive to return all calls within one business day.