According to a recent National Research Council report, maps of flood danger in the United States are based on data that are decades old. Many are calling for an update.
"Maps being used to calculate flood danger in the United States rely on data that are decades out of date, according to a report that calls for a new national program to remap land levels."
"The most immediate need is for the Federal Emergency Management Agency's flood-mapping program. Those maps are used by mortgage companies and FEMA's National Flood Insurance Program to determine whether property owners should be required to purchase flood insurance."