How is a 100-year floodplain defined?

A 100-year floodplain is defined as an area that has a 1% chance of flooding in any given year. This designation is used in floodplain management, urban planning, and insurance underwriting to assess flood risk. It is important to understand that the term "100-year" does not mean that flooding occurs only once every century; rather, it reflects the statistical probability that any given area could experience flooding during a particular year.

This definition helps communities and individuals identify regions that may be at risk of flooding, enabling better preparedness and risk management. It guides zoning laws, building codes, and the construction of flood control measures. Understanding this distinction is crucial for those involved in the planning and management of On-Site Sewage Facilities (OSSF), as flooding can significantly impact sewage systems and public health.