Land records · Parcel maps · October 6, 2026
What Is a Base Flood Elevation? BFE on Flood Maps
What is a base flood elevation? The height floodwater should reach in a 1 percent annual chance flood, and how BFE affects insurance and building rules.
What is a base flood elevation? The base flood elevation, or BFE, is the elevation that floodwater is expected to reach during the base flood, a flood with a 1 percent chance of being equaled or exceeded in any given year. BFEs are shown on FEMA Flood Insurance Rate Maps in many high-risk zones, such as Zone AE, and are measured relative to a vertical datum such as NAVD 88. The BFE matters for flood insurance rates and for how high new or substantially improved buildings must be elevated. This page is general land-records background, not legal advice.
Where to find the BFE
- Flood Insurance Rate Map (FIRM): wavy lines labeled with elevations in AE zones, or a number in parentheses within a zone.
- Flood Insurance Study: profiles and tables with flood elevations along streams.
- Local floodplain administrator: can provide BFEs and determinations.
- Elevation certificate: lists the BFE for the building site.
See how to read a FEMA flood map.
Zones with and without BFEs
| Zone | BFE shown? |
|---|---|
| AE, AH, A1–A30 | Yes |
| VE (coastal high hazard) | Yes |
| A (approximate) | No, may need to be determined |
| X | No (moderate to minimal risk) |
See flood zone AE vs X.
How the BFE affects building
Communities in the National Flood Insurance Program require the lowest floor of new and substantially improved residential buildings in special flood hazard areas to be at or above the BFE. Many communities add freeboard, requiring floors 1 to 3 feet above the BFE. Nonresidential buildings may be floodproofed instead.
How it affects insurance
Flood insurance pricing considers flood risk, and the relationship between a building’s elevation and the BFE has traditionally been a major factor. A building well above the BFE generally carries lower risk. An elevation certificate documents the lowest floor and other elevations compared with the BFE.
Datum matters
BFEs are given in a vertical datum, usually NAVD 88 on newer maps or NGVD 29 on older ones. Comparing a building elevation in one datum with a BFE in another gives wrong results. See what is NAVD 88.
BFE vs depth
The BFE is an elevation, not a depth. If the BFE is 102 feet and the ground at your house is 99 feet, the base flood could be about 3 feet deep there. Zone AO areas show depths instead of BFEs.
When maps change
BFEs can change when FEMA updates maps or when a Letter of Map Revision is issued. Preliminary maps are often available before they become effective. See what is a LOMR.
Bottom line
The base flood elevation is the height floodwater is expected to reach in a 1 percent annual chance flood. It appears on FEMA maps in AE and VE zones, sets minimum floor heights for new construction in flood areas, and affects insurance. Always check the datum before comparing elevations. Find county flood layers via the Platbookmapper map.
What is a base flood elevation FAQ
What does BFE mean on a flood map?
Base flood elevation, the expected flood height in a 1 percent annual chance flood.
Is the base flood elevation the same as flood depth?
No. BFE is an elevation; depth is the BFE minus ground elevation.
How high must a house be above the BFE?
At least at the BFE in participating communities, often 1 to 3 feet above with local freeboard.
Where can I find my property’s BFE?
On the FEMA flood map, the Flood Insurance Study, or from the local floodplain administrator.
Does Zone X have a BFE?
No. Zone X areas are outside the 1 percent annual chance floodplain.