bfE

BFE, or Base Flood Elevation, is a term used in floodplain management and civil engineering to describe the computed elevation to which floodwaters are expected to rise during a base flood, typically defined as a flood event with a one‑percent chance of occurring in any given year (the 100‑year flood). The BFE is expressed as a height above mean sea level and is derived from hydraulic analyses that consider topography, rainfall, river flow, and other hydrologic factors. It serves as a regulatory benchmark for the design and construction of structures in flood‑prone areas, guiding decisions on building elevation, floodproofing measures, and land‑use planning.

In the United States, the Federal Emergency Management Agency (FEMA) publishes BFEs in Flood Insurance Rate Maps (FIRMs), which are used by local governments to enforce building codes and by property owners to assess flood risk and obtain insurance. The National Flood Insurance Program (NFIP) requires new construction in designated flood zones to have the lowest floor elevated at least one foot above the BFE, unless an alternative flood‑resistant design is approved. While the BFE reflects a statistical average, actual flood depths can vary due to local conditions, climate change, and extreme weather events. Consequently, engineers and planners often incorporate freeboard—additional elevation above the BFE—to provide a margin of safety. The concept of BFE continues to evolve as more precise modeling techniques and higher‑resolution terrain data become available.