What is defined as the flood having a 1% chance of being equaled or exceeded in a given year?

The flood that has a 1% chance of being equaled or exceeded in a given year is referred to as the Base Flood. This term is critical within floodplain management and is commonly used in the Federal Emergency Management Agency (FEMA) guidelines. The Base Flood is often the benchmark used to assess flood risk and determine necessary floodplain management regulations.

Understanding this concept is essential for various stakeholders, including builders, planners, and inspectors, as it informs them about potential flood risks and the need for appropriate design and construction practices in flood-prone areas. This understanding also aids in the development of flood insurance rates and local zoning laws to maximize safety and minimize economic loss from flooding.

The associated terms like Design Flood refer to specific standards set for construction, while Flood Hazard Area and Design Flood Elevation pertain to broader planning and regulatory frameworks, but the 1% annual chance specifically identifies the Base Flood.