In the United States, a flood zone is a geographically defined area with a specific level of flood risk, as designated by the Federal Emergency Management Agency (FEMA) on its Flood Insurance Rate Maps. These zones are used to determine flood insurance requirements, building codes and land-use planning. Each flood zone reflects the probability of flooding in any given year — often referred to as the “100-year floodplain,” or an area with a 1 in 100 annual chance of flooding. While the term “flood zone” in the U.S. has a specific regulatory and insurance-based meaning, other countries use comparable systems for flood hazard mapping and risk assessment. For example, “flood risk areas” in the U.K. or “inundation zones” in parts of Europe — though the metrics and legal implications differ.
