Base flood elevation (BFE) is a measurement used by the Federal Emergency Management Agency (FEMA) to determine the likelihood of a flood in a particular area. The National Flood Insurance Program (NFIP) also uses BFE to develop local building codes and set flood insurance rates.
What is base flood elevation?
Base flood elevation is the level that water is expected to reach during a 100-year flood, also called a “base flood.” That means there's a 1% chance of a flood at that level happening in any given year. BFE is calculated using information from hydrological modeling, topographic mapping, and historical flood data.
A common misconception is that base flood refers to a flood that only happens once every 100 years. In reality, base floods can happen more than once within a short period of time, even in subsequent years.
FEMA maps base flood elevations for several flood zones, including:
- AE
- AH
- A1–A30
- AR
- AR/A
- AR/AE
- AR/A1–A30
- AR/AH
- AR/AO
- V1–V30
- VE
BFE is also a key factor in determining Special Flood Hazard Areas (SFHAs), which are the highest-risk flood zones. SFHAs have at least a 1% annual chance of flooding. Homes in SFHAs with a federally backed mortgage are required to have flood insurance.
What’s the difference between BFE and ground elevation?
For homeowners, it’s important to understand the difference between BFE and ground elevation. Ground elevation is the height of the land your home is on. BFE is the predicted height that surface water will reach during a 100-year flood.
To mitigate flood risk, your home’s ground elevation should be at or above the BFE.
How to find the base flood elevation for a property
If you’re wondering about your home’s BFE, here are some ways you can find it.
FEMA Flood Map Service Center (MSC)
The easiest way to find the BFE of your property is to use FEMA’s Flood Map Service Center. Enter your address, and it will populate the map with your flood zone and BFE, if there is one. BFE is shown as EL plus a number (i.e., EL 10). This number represents the expected height rounded to the nearest foot. So, EL 10 represents a BFE of roughly 10 feet.
You can also use FEMA’s MSC to find a Flood Insurance Rate Map (FIRM). If your home is in an SFHA, it will show up in a shaded or colored area on the map. In these zones, flood insurance is mandatory if you have a federally backed mortgage.
Elevation certificates
The most accurate way to determine your home’s BFE is to check the elevation certificate (EC), if the property has one. An EC is typically created by a licensed surveyor and includes the property’s ground elevation, flood zone designation, and building characteristics, like the lowest floor height.
An EC is considered the best way to determine a home’s relationship to the BFE because it uses the home’s precise measurements, not generalized flood maps. ECs are used to determine flood insurance premiums and are sometimes required to prove that your home complies with local building codes for flood mitigation.
Local community officials
Another way to determine the BFE of your property is to contact local community officials, like building departments or floodplain managers. They’re often responsible for working with FEMA to develop flood maps and enforce building codes in SFHAs.
Local floodplain managers can also help you better understand your home’s FEMA flood zone or BFE if you’re not sure what it means for your property and insurance requirements.
Why base flood elevation matters for homeowners
Not every home has a BFE, but if you’re a homeowner, it’s important to find out whether your property has one. If your house has a BFE, here are some things that it can impact:
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Insurance premiums: Insurance companies compare the BFE in your area to the elevation of the lowest floor in your home to estimate the chances of flood damage. This is important for determining flood insurance premiums. If your home’s lowest level is above the BFE, then floodwaters are less likely to reach it, and the insurer may charge a lower rate.
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Building and remodeling requirements: If you’re planning to build a new house or renovate your home, make sure to check the BFE first. Local building codes often require new home construction or substantial improvements to be built at or above the BFE to reduce the likelihood of flood damage.
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Freeboard: Another consideration when building or renovating your home is whether you should incorporate freeboard as another layer of protection against flooding. Freeboard is a buffer of additional height built in to account for uncertainty and reduce risk. It typically adds between one and three feet to the BFE, which can improve flood resiliency and reduce your flood insurance premiums.
Base flood elevation vs. other flood terms
If your home is in a flood zone, it’s important to understand common terminology. Here are some other terms that are related to BFE, and how to distinguish them:
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Hydrostatic pressure: Hydrostatic pressure is the force that standing flood water puts on your home’s foundation and walls. It’s used to determine how much damage the water is expected to cause in a flood event. BFE refers to how high flood waters are estimated to come up during a 100-year flood event, not how much damage the flood could cause.
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Flood zones: A flood zone is an area that FEMA has designated as having some chance of flooding based on historical data and topographic mapping. BFE dictates whether a specific property is in a high-risk or moderate-to-low-risk flood zone. Areas that are outside the 100-year floodplain don’t typically have a mapped BFE.
Frequently asked questions
Does base flood elevation ever change?
Yes, base flood elevations can change when FEMA updates Flood Insurance Rate Maps based on new flood data, land development, or changing weather patterns. A change in BFE can potentially move a property into or out of a high-risk flood zone, so it’s important to check your home’s BFE periodically.
What happens if my home is below the base flood elevation?
If your home is below the BFE, you could pay much higher flood insurance premiums due to the increased likelihood of flood damage. If you’re planning to renovate your home, you might also have to meet stricter building code requirements for floodproofing or elevating the foundation, which can increase building costs.
Is base flood elevation the same as the 100-year flood level?
BFE is the elevation of a given area that’s associated with the 100-year flood. It’s the estimated height that surface water will reach during a 1% annual chance flood.
Do I need an elevation certificate if I’m not in a high-risk zone?
Elevation certificates aren’t typically required if you don’t live in a high-risk flood zone. However, getting an elevation certificate can sometimes help prove your home’s flood resilience. That can potentially lower your flood insurance premiums, even in moderate-risk areas.
What is the difference between base flood elevation and DFE?
Base flood elevation is the predicted level that flood waters will reach during a base flood. Design flood elevation (DFE) is the estimated elevation of the highest possible flood level in a given location. DFE usually equals the BFE plus freeboard — freeboard is a buffer of additional height built into the calculation to account for uncertainty and reduce risk — so it's a higher value than BFE.
