What Is Base Flood Elevation and Why Does It Matter?

When it comes to evaluating flood risk, one number can change everything: your Base Flood Elevation (BFE). This FEMA-designated measurement is more than just a line on a map—it can determine your insurance rates, your construction requirements, and your home’s resilience in a disaster. Yet many homeowners and even professionals struggle to understand what it means, how it works, or how to find it.  

What Is Base Flood Elevation?

The Base Flood Elevation is the computed height that floodwaters are expected to rise during a 1% annual chance flood—commonly known as the “100-year flood.” FEMA calculates this level using a combination of hydrologic models, hydraulic studies, and historical flood records as part of their Flood Insurance Study (FIS).

In short, the BFE is the reference point used to compare how high floodwaters might rise versus your structure’s elevation above sea level. Properties built below this elevation face greater risk and higher insurance costs.  

How Is BFE Determined?

BFEs are calculated by FEMA and local authorities using hydrologic and hydraulic analyses of regional watersheds. These studies are documented in FEMA’s Flood Insurance Studies and visualized in Flood Insurance Rate Maps (FIRMs). These models factor in:

• Rainfall and runoff trends
• Soil saturation
• River and stream channel topography
• Historical flooding data

Zones AE and VE, for example, are FEMA flood zones that typically include BFE information, whereas Zones A and V do not. (V is to VE as A is to AE: both pairs share similar risk factors, but only the “E” zones have BFE data.) Knowing whether your zone has this information available is the first step to making informed insurance and construction decisions.  

BFE vs. Your Property Elevation

Knowing the BFE alone isn’t enough. What truly matters is how your structure’s lowest floor elevation compares to the BFE. This is where an Elevation Certificate comes in.

If your home is two feet below the BFE, you’re likely to face significantly higher premiums—or worse, be deemed uninsurable for flood coverage through some private carriers. By contrast, homes built above BFE may qualify for lower NFIP premiums or be eligible for a Letter of Map Amendment (LOMA) to remove the mandatory insurance requirement.  

How to Find Your BFE

FEMA’s Flood Map Service Center provides digital FIRMs and FIS data. To find your BFE:

1. Visit the FEMA Map Service Center
2. Enter your property’s address
3. Review the location of the pin on the map that opens to ensure the address search found the correct property. You can also zoom in to verify accuracy.  
4. Look for your flood zone designation (e.g., AE, V, A)
5. Where BFE is available, it is shown directly on the map and in the legend. For more details, consult the FIS report for your area.  

If no BFE is listed, for instance, in Zone A or unmapped rural areas, consult a licensed surveyor or floodplain engineer. A professional can prepare an Elevation Certificate and conduct site-specific modeling to determine BFE for that location.

Why Missing BFE Data Increases Your Risk

If your zone lacks a defined BFE, insurers often apply conservative assumptions. This can translate to higher rates, limited policy options, or costly force-placed coverage from your mortgage lender.

Missing BFE data also complicates permitting and construction in flood zones, as communities must rely on estimated or default elevations. This uncertainty poses both regulatory and financial risks.

Tammy Schwartz, Senior Director of Data and Analytics at Guidewire, notes:

"Missing BFE doesn’t mean missing flood risk. We’ve seen underwriters price policies much higher when BFE is absent—especially in repeat loss areas."

BFE and Flood Insurance Underwriting

Insurers use BFE in underwriting decisions to determine eligibility and assign premiums under FEMA’s Risk Rating 2.0 framework. Properties below BFE may be flagged for increased risk and routed through stricter underwriting tiers. Those with elevation certificates proving their lowest floor is above BFE could qualify for reduced premiums or exemptions.

In FEMA’s mapped zones, some of the most common designations include:

• Zone AE and VE: Typically include defined BFE and wave height data.
• Zone A: High risk, but without specific BFE—owners must often obtain their own data.
• Zone X: Moderate to low risk, usually outside Special Flood Hazard Areas, with no BFE.

What If Your BFE Is Missing?

Homeowners in Zone A or unmapped areas have several options:

• Hire a licensed land surveyor to complete an Elevation Certificate
• Use the certificate to apply for a LOMA or Letter of Map Revision Based on Fill (LOMR-F)
• Request FEMA review through the NFIP’s appeals process
• Use private flood modeling tools for supplemental data, especially if the property is outside FEMA’s digital coverage

Real-World Impact: Construction and Cost

Low BFE values don’t just influence insurance—they also trigger construction constraints. In many communities, homes must be built one to three feet above BFE to meet local floodplain management rules. Failing to meet these standards can delay permits or result in expensive retrofits later.

If you plan to build, renovate, or sell a home in a flood zone, knowing your BFE could prevent tens of thousands of dollars in hidden costs.

Why BFE Data Is Becoming More Critical

As climate change drives more intense rainfall and sea level rise, lenders are increasingly enforcing flood coverage requirements. Insurers and regulators are also shifting to more granular flood risk models that rely heavily on BFE and elevation data. While FEMA works to update flood maps, the process can be lengthy, meaning some areas may go years without revised information.

Take the Next Step

Whether you’re evaluating flood insurance, planning construction, or reviewing a property investment, your BFE matters. Knowing your elevation in relation to FEMA’s 1% annual chance flood level could save you money, strengthen your home, and protect your future.
Take the HazardHub Quiz to discover your property’s flood risk and learn what elevation-based changes could lower your premiums.