What does a 100-year floodplain indicate?

A 100-year floodplain indicates an area that has a 1% chance of flooding in any given year. This terminology derives from statistical analysis of historical flood data, which suggests that over a period of 100 years, there is a 1% probability that such a flood will occur in any single year. This does not mean that a major flood will happen precisely every 100 years; rather, it reflects the likelihood of flooding based on past occurrences. A key aspect of understanding this concept is recognizing that the "100-year" designation refers to the frequency and risk associated with flooding, rather than a literal timeframe. Thus, this classification serves as an important tool for land use planning, insurance underwriting, and risk assessment for properties and developments situated within these designated flood zones.