The term “100-year flood” is misleading. It is not the flood that will occur once every 100 years; rather, it is the flood that has a one percent chance of being equaled or exceeded annually. It is based on probabilities, not predictions. Thus, the 100-year flood could conceivably occur multiple times in a year, or not at all over a period of 150 years or more. Because the term “100-year flood” is misleading, FEMA has also defined it as the one-percent-annual-chance flood. The “one-percent-annual-chance flood” is the term that is now used by most Federal and State agencies and by the National Flood Insurance Program (NFIP). It can also be interpreted as 26% chance of flooding over the life of a 30-year mortgage.