Base Flood Elevation (BFE) is one of the most fundamental concepts in floodplain management, yet it’s often misunderstood or oversimplified. If you’re preparing for the Certified Floodplain Manager (CFM®) Exam, understanding BFE—both in theory and application—is essential.
Definition of BFE
The Base Flood Elevation is the elevation (typically in feet above mean sea level) that floodwaters are expected to reach during a base flood, which is defined as a flood that has a 1% chance of occurring in any given year—commonly referred to as the 100-year flood.
BFEs are determined through hydrologic and hydraulic modeling (commonly HEC-HMS and HEC-RAS) and are typically shown on FEMA’s Flood Insurance Rate Maps (FIRMs).
Where BFE Shows Up in Practice
You’ll encounter BFEs in several places:
- FEMA FIRMs: BFEs are displayed as lines with accompanying elevations on detailed flood maps (Zones AE and VE).
- Elevation Certificates: Used for flood insurance, development permitting, and LOMAs; the structure’s lowest floor elevation is compared against the BFE.
- Development Regulations: Communities participating in the NFIP require the lowest floor of new or substantially improved buildings in SFHAs to be at or above the BFE.
- Design Projects: For infrastructure like culverts, bridges, and levees, BFE affects sizing, location, and required freeboard.
The Base Flood Elevation dictates the height to which a building must be elevated to comply with Floodplain Management Regulations. Above is an example of a home in New Bern, North Carolina elevated to the BFE.
How is BFE Determined?
BFE is calculated using models that simulate rainfall, runoff, and channel flow. Here’s a simplified breakdown:
- Hydrology – Determine how much water results from a 1%-annual-chance storm using models like HEC-HMS.
- Hydraulics – Model the movement of that water through rivers, streams, and floodplains using tools like HEC-RAS.
- Mapping – Use results to delineate flood zones and plot BFEs on FIRMs.
In areas without detailed studies, approximations may be used (Zone A), but detailed studies (Zones AE, VE) include computed BFEs.
Why You Must Master BFE for the CFM Exam
Expect the exam to test you on both conceptual and applied knowledge of BFE:
- Interpreting FIRMs and identifying BFE for specific sites
- Determining compliance with elevation requirements
- Understanding the role of BFEs in Letter of Map Change (LOMC) processes
- Applying BFE in floodplain development scenarios
You’ll need to be comfortable navigating map panels, identifying regulatory floodways, and comparing structure elevations to BFEs.
Heating Ventilation and Air Conditioning (HVAC) and Mechanical Equipment is required to be elevated to or above the Base Flood Elevation (BFE). Example of this on a beachfront property in Coastal Delaware.
Pro Tip: BFE Is Not Freeboard
Many confuse BFE with freeboard. Freeboard is the additional elevation above BFE required by local or state regulations—usually 1 to 3 feet—to provide a safety buffer. The CFM exam may test your understanding of this difference in regulatory or design scenarios.
Learn BFE the Right Way with Civil Engineering Academy
The Ultimate Floodplain Manager Review Course offered by Civil Engineering Academy goes deep into the concept of Base Flood Elevation—breaking down the math, the maps, and the regulatory implications in a way that makes sense.
- Detailed videos that walk through FIRMs, profiles, and elevation certificates
- Real-world examples that show how BFEs are calculated and used
- Practice problems that simulate CFM exam scenarios
Tips for remembering key definitions, thresholds, and standards
Why This Matters
Knowing the Base Flood Elevation isn’t just about passing a test—it’s about protecting lives and property. Whether you’re reviewing development plans, helping a homeowner with flood insurance, or working on a major infrastructure project, your understanding of BFE could directly impact flood risk outcomes in your community.
If you want to feel confident—not just memorized—about BFE and every other key topic on the exam, start the Ultimate Floodplain Manager Review Course today.
Author: Matt Fanghella, PE, CFM