What Are Floodplains?
Floodplains are established by determining the areas that flood when creeks, bayous, and river waters exceed their banks. In most cases, floodplains are determined by their chance to flood in the future, hence the 10, 100, and 500 year floodplain references. Many times these terms can be confused as the risk of flood is determined over a long period of time. The Harris County Flood Control District in Houston has broken these floodplains down into one year increments, and given a chance of possible flooding based on a one year time frame for each floodplain. • 10 Year Floodplain – 10% chance of flooding in a single year – 95% chance of flooding in a 30 year mortgage. • 100 Year Floodplain – 1% chance of flooding in a single year – 26% chance of flooding in a 30 year mortgage. • 500 Year Floodplain – 0.2% chance of flooding in a single year – 6% chance of flooding in a 30 year mortgage. As you can see, when the percentages are broken down into the yearly level they are much easier to un
