What is a Flood Zone? Zoning Definition

A flood zone is an area mapped by the Federal Emergency Management Agency (FEMA) that shows the probability of flooding. These zones are shown on Flood Insurance Rate Maps (FIRMs) and are designated by letters. The most common high-risk zones are Zone A (riverine flooding) and Zone V (coastal flooding with wave action), both of which represent areas with a 1% or greater chance of flooding in any given year — commonly called the "100-year floodplain." Zone X represents areas with lower flood risk.

If your property is located in a high-risk flood zone (Zone A or V) and you have a federally backed mortgage, your lender will require you to carry flood insurance through the National Flood Insurance Program (NFIP) or a private insurer. Properties in moderate- or low-risk zones are not required to carry flood insurance but can still flood, and coverage is recommended.

Flood zones significantly affect what and how you can build. Local floodplain ordinances, which communities must adopt to participate in the NFIP, require that new construction and substantially improved structures in high-risk zones be elevated to or above the Base Flood Elevation (BFE). Additional requirements may include flood-resistant materials, proper anchoring, and restrictions on enclosing space below the BFE. Many communities add freeboard — extra height above the BFE — for additional safety.

Before purchasing property or planning a construction project, check the FEMA flood map for your area. You can look up flood zones at FEMA's Flood Map Service Center online. If you believe your property's flood zone designation is incorrect, you can apply for a Letter of Map Amendment (LOMA) or Letter of Map Revision (LOMR) to have it changed.