What is a typical characteristic of a 100-year floodplain?

A typical characteristic of a 100-year floodplain is that it has a 1% chance of flooding each year. This designation indicates that over a long period, such as 100 years, there is a cumulative probability of 100% that it will experience a flood event at least once, but in any single year, the statistical likelihood of flooding still remains 1%. This information is critical for land use planning, insurance, and real estate development, as it helps assess the risk associated with flooding.

High elevation terrain would not accurately represent a 100-year floodplain, as such areas would not be subject to the same flood risk. Complete flood protection measures being in place would also not define a 100-year floodplain; while flood mitigation strategies may be employed, the term refers specifically to the probability of flooding rather than the presence of protective measures. Lastly, year-round waterlogged conditions would suggest a permanently saturated area, which is different from the intermittent flooding associated with a 100-year floodplain that occurs under specific rain or storm conditions.