Flood maps are issued by The Federal Emergency Management Agency (FEMA) as an end result of a general study of a large area. This study does not evaluate individual properties and is very broad based in nature. These areas are then determined to be Special Flood Hazard Areas (SFHA). A SFHA is an area that has been determined to have a 1% annual chance of flooding in 100 years and FEMA requires mandatory flood insurance on property located in a SFHA. Your property was not studied by FEMA individually. This is why there is a 60% margin of error in the flood maps. Flood maps are updated every few years.