What is the probability of flooding within a 100-year floodplain?

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.  

Show All Answers

1. What is the Federal Emergency Management Agency?
2. What is a Floodway?
3. What is a floodplain, and what is a flood?
4. What is the National Flood Insurance Program?
5. What is a Flood Insurance Rate Map? What is the importance of a Special Flood Hazard Area and what are flood zones?
6. What is the probability of flooding within a 100-year floodplain?
7. Is there really a need for flood insurance?
8. My house is in a Floodplain? What do I need to do?
9. Who has to buy Flood Insurance?
10. What is a Preferred Risk Policy? Can this save property owners money?
11. What is an elevation Certificate?