This information is based on the FEMA Flood Insurance Rate Maps (FIRMs), which are developed after conducting a detailed Hydrologic Engineering analysis called the Flood Insurance Study. In this analysis the chances of occurrence of a flood are also determined statistically. For example, when we say that a property is in a 100-year Flood Zone, this means that statistically the chance of occurrence of Flood on this property is, in one year is 1% or greater and is never less than 1%.