FEMA has two applications to display various flood related data in Google Earth.
Stay Dry - This is the simpler of the two applications. When you start Stay Dry, you’ll see an overview map of the US that shows which areas of the country have coverage available. If the area you are interested in is shaded in purple, then there should be flood data available in Google Earth. As you zoom in, the layers will change to display the flood zone data.
FEMA NFHL - This application displays a large amount of data and may be a little difficult to figure out without spending some time reading the instructions.
These are both very useful tools. The FEMA website has a lot more information, including detailed instructions for both applications. I would highly recommend reading the instructions before using these applications for any kid of official use.