Glossary of Flood Terms

Glossary of Flood Terms | Flood Zone Definitions | Availability

Flood Terminology:

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The Federal Emergency Management Agency (FEMA) provides no digital maintenance for the 12,000 map revisions it issues annually-but FloodMap does! FloodMap reflects all FEMA revisions. The entire database is refreshed quarterly to ensure accuracy, currency and investment value. When you perform a lookup on the RiskMeter Online, you’ll receive the most recent digital flood map information available.

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

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

Base Flood: Defined by FEMA as 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 height of the base (100-year) flood in relation to a specified datum, usually the National Geodetic Vertical Datum of 1929 or North American Vertical Datum of 1988. Generally speaking, this is the elevation of the 100-year flood waters 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. For example, if the property's foundation was at an elevation of 125 feet and the BFE was 131 feet, then one might infer that the 100-year depth of flooding would be approximately 6 feet.