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Flood Glossary

The definitions below will help define terms commonly used by FEMA in communications with the public.

Visit Flood Information and/or Flood Resources for more information.

Base Flood Elevation (BFE): The elevation, or height, a flood may reach during the base flood. The base flood is also called the 1% annual-chance flood or 100-year flood.

Conditional Letter of Map Revision (CLOMR): A letter from the Federal Emergency Management Agency (FEMA) saying that a proposed project would change a flooding source, such as a creek or river, and that it may modified an existing floodplain.

Letter of Map Revision (LOMR): A letter from FEMA that says a parcel of land or proposed structure will not be flooded by the base flood. This usually follows a project that included a CLOMR.

Flood Insurance Rate Map (FIRM): This map shows Special Flood Hazard Area (SFHA) which has been found to be subject to a base flood or greater chance of flooding. The FIRM is used to set flood insurance rates and to help with floodplain management.

Floodway: The portion of the floodplain that includes the channel of a river (or other flood source) and the area likely to be flooded in a base flood.

Special Flood Hazard Area (SFHA): An area with special flood hazards as shown on a Flood Insurance Rate Map (FIRM). In Washington County's FIRMs, these areas are Zone A and Zone AE. SFHAs are where the National Flood Insurance Program's (NFIP) floodplain management regulations are enforced and where flood insurance is mandatory. SFHAs are commonly referred to as the 100-year floodplain or the 1% annual chance flood area.