The term 100-year flood is misleading. It is not the flood that will occur once every 100 years. Rather it is a flood that has a 1% chance of being equal to or exceeding each year. Because of this, the 100-year flood could occur more than once in a relatively short period of time.
According to FEMA.gov and the NFIP, another way to analyze the flood risk is to contemplate the odds that a 100-year flood will occur sometime during the life of a 30-year mortgage. A structure located within a Special Flood Hazard Area (SFHA), shown on a National Flood Insurance Rate Map, has a 26% chance of suffering flood damage during the term of a 30- year mortgage. Even these numbers do not convey the true flood risk since it focuses on the larger, less frequent floods. If the topography of a house is low enough, it may be subject to the 10- or 25-year flood. Assuming a 30-year mortgage, it may have a 26% chance of being affected by a 100-year flood, but the probability is 96% for the structure to be affected by a 10-year flood. mortgage. Property owners outside the 100-year floodplain are free of regulatory requirements, but not the risk. Federally backed flood insurance is available to property owners outside the 100-year floodplain as well.