Glossary5 terms

Flood & Natural Hazards

FEMA flood zone, SFHA, Base Flood Elevation and 2 more, each with its own link.

FEMA flood zone: The Federal Emergency Management Agency's classification of flood risk for any U.S. property. Common designations: Zone X (minimal hazard, no insurance required), Zone A (inside the Special Flood Hazard Area, the 1-percent-annual-chance flood per FEMA's flood zone definitions, fema.gov/glossary/flood-zones, read 2026-10-19; insurance usually required), Zone AE (detailed elevation study), Zone V/VE (coastal high-hazard with velocity waves), Zone D (undetermined). Flood zone affects insurance cost, building codes, and property value.
SFHA (Special Flood Hazard Area): A FEMA-designated flood zone inundated by the flood with a 1-percent chance of being equaled or exceeded in any given year, the '100-year floodplain' (FEMA flood zone definitions, fema.gov/glossary/flood-zones, read 2026-10-19). Includes Zones A, AE, AH, AO, V, and VE. Flood insurance is mandatory for any federally-backed mortgage on an SFHA property. New construction in an SFHA must typically be elevated above Base Flood Elevation (BFE) plus a local freeboard margin. Buildability flags SFHA status in every Report.
Base Flood Elevation (BFE): The elevation, in feet above mean sea level, that floodwaters are predicted to reach during the 1-percent-annual-chance flood, the 100-year flood (FEMA flood zone definitions, fema.gov/glossary/flood-zones, read 2026-10-19). BFE is established by FEMA flood maps for properties in flood zones. New construction in a flood zone must typically be built at or above BFE plus a freeboard margin set by local code.
WUI (Wildland Urban Interface): The geographic area where development meets undeveloped fire-prone vegetation. WUI properties are the highest-risk category for wildfire and face strict building code requirements (Class A roofing, ember-resistant vents), defensible space clearance (typically 100 feet), and significantly higher insurance premiums. Many insurers have pulled out of high-WUI markets in California and Colorado.
FHSZ (Fire Hazard Severity Zone): California's three-tier classification of wildfire risk: Moderate, High, and Very High Fire Hazard Severity Zone. Properties in Very High FHSZ must comply with Chapter 7A of the California Building Code (fire-resistant materials) and maintain defensible space. CalFire maintains the official FHSZ maps; other western states use similar classifications.

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