FEMA Base Flood Elevation (BFE)

1. What is it?

Base Flood Elevation (BFE) is a FEMA-derived metric representing the elevation (typically in feet) to which floodwater is anticipated to rise during a 1-in-100-year flood event. It is currently the most commonly adopted metric for measuring flood elevation by insurers in the US.

BFE is derived from FEMA’s hydraulic models and is only present in zones where detailed studies have been conducted, primarily AE, AH, AO, and VE flood zones (for more information about flood zones see FEMA National Flood Hazard Layer). It forms the basis for regulatory floodplain management and insurance rating under the National Flood Insurance Program (NFIP).

BFEs are presented as cross-sections along modelled watercourses and as a result can be spatially sparse. To address this, Addresscloud supplements FEMA BFE data with additional calculated attributes to plug gaps in data where BFEs are not present as well as providing context on distance to the cloest BFE point.

Here is an example of what the BFE points look like. The BFEs are represented by the blue lines.

2. How can I use it?

Addresscloud's BFE data allows insurers to:

• Determine flood risk exposure at a property-level resolution
• Inform flood insurance pricing and eligibility decisions
• Support compliance with federal and local building regulations
• Assess proximity to known flood hazard sources
• Improve accuracy when detailed BFE data is unavailable, thanks to Addresscloud’s interpolation and proximity calculations

3. How is the data created?

FEMA BFE

BFE data is generated by FEMA through hydraulic modelling, often based on cross-section surveys of watercourses. However, these surveys can be decades old and spaced widely apart, limiting their usefulness at fine spatial resolutions.

Interpolated BFE (Addresscloud Enhancement)

To improve coverage, Addresscloud computes an interpolated BFE using:

• Surrounding FEMA BFE points
• Ground elevation data from the USGS

This allows an approximate flood elevation to be assigned to properties even where no FEMA point is directly present.

Distance to BFE

When the nearest BFE survey point is far from the property, Addresscloud also includes a distance metric, giving users a sense of how reliable or local the result is.

4. Are there any limitations?

• Zonal Restrictions: Only zones AE, AH, AO, and VE contain BFE data. Zones A and V lack detailed modelling; zones X, D, B, and C are not considered high-risk and therefore excluded from BFE surveys.
• Data Age: Some BFE surveys can be decades old
• Sparse Sampling: FEMA cross-section intervals can lead to BFE values being separated by long distances
• Interpolation Caveats: Interpolated BFE values are estimations, not direct survey results

5. What data points are available?

The following BFE attributes are available under our US Flood dataset (usflod)

• bfe_interp: The interpolated Base Flood Elevation (BFE) in metres
• bfe_interp_ft: The interpolated Base Flood Elevation (BFE) in feet
• bfe_fema: The FEMA Base Flood Elevation (BFE) in metres
• bfe_fema_ft: The FEMA Base Flood Elevation (BFE) in feet
• bfe_dist: The distance to the nearest BFE (from either interpolated or FEMA data) in metres
• bfe_dist_ft: The distance to the nearest BFE (from either interpolated or FEMA data) in feet

6. Where can I find out more?

Further information on our US Flood Product can be found on our US Flood help page.

To find out more about Flood Zones you can visit our National Flood Hazard Layer help page.

For additional information and technical documentation, please refer to the Addresscloud API Documentation.

For support and inquiries, contact Addresscloud through their Help Center.