BFE

The Base Flood Elevation is the height, referenced to a fixed vertical datum, that floodwater is expected to reach or exceed during the one-percent-annual-chance flood at a given location. FEMA publishes BFEs within mapped flood zones, and they anchor both regulation and pricing: construction standards in flood zones require lowest floors or flood-proofing at or above elevations keyed to the BFE, and flood-insurance pricing responds to how a structure's elevation compares to it.

The difference between a building's lowest-floor elevation and the BFE — its freeboard, positive or negative — is among the most decision-relevant flood metrics for a specific property: two neighbors in the same mapped zone can face very different expected losses because their ground and floor elevations differ.