Glossary of Flood Terms


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100-year flood: The flood having a 1% or greater annual probability of occurring.

500-year flood: The flood having a 0.2% or greater annual probability of occurring.

Base Flood: A flood having a 1-percent probability of being equaled or exceeded in any given year; also referred to as the 100-year flood.

Base Flood Elevation (BFE): Defined by FEMA as the elevation of the crest of the base or 100-year flood relative to mean sea level. BFE is not depth of flooding. To determine depth of flooding, you would need to subtract the lowest elevation of a particular property from the BFE.

Community Number: A 6-digit designation identifying each NFIP community. The first two numbers are the state code. The next four are the FIMA-assigned community number. An alphabetical suffix is added to a community number to identify revisions in the Flood Insurance Rate Map for that community.

Flood Insurance Rate Map (FIRM): An official map of a community, on which the Federal Insurance and Mitigation Administration has delineated both the Special Flood hazard Area's and the risk premium zones applicable to the community. Most FIRM's include detailed floodplain mapping for some or all of a community's floodplains.

Floodplain: Any land area susceptible to being inundated by floodwaters from any source.

Freeboard: A margin of safety added to the base flood elevation to account for waves, debris, miscalculations, or lack of data.

Panel: Panel number is numerical designation used to identify the FIRM Map associated with a given area. The first six digits of the Panel number is the community number.

Panel Date: This is the date recorded in the FEMA FMSIS database, which is associated with the given Panel Number.

Repetitive Loss Property: A property for which two or more National Flood Insurance Program losses of at least $1,000 each have been paid within any 10 year period since 1978.

Special Flood Hazard Area (SFHA): An area designated as within a "Special Flood Hazard Area" (or SFHA) on a FIRM. This is an area inundated by 1% annual chance flooding for which BFEs or velocity may have been determined. No distinctions are made between the different flood hazard zones that may be included within the SFHA. These may include Zones A, AE, AO, AH, A99, AR, V, or VE.