100-year floodplain

A 100-year floodplain is an area that has a 1% chance of experiencing a flood of a certain severity in any given year. It doesn’t mean such a flood happens only once every 100 years; rather, over long periods, flooding at that level is statistically likely to occur once every century. These zones are identified through flood risk assessments and help inform land use planning, insurance requirements, and construction standards. Being in a 100-year floodplain means your property has a significant, but not constant, risk of flooding, especially during particularly heavy rain or storm events.