Flood Maps:

Harris County Flood Education Mapping Tool
Harris County only by address, slow to update new FIRMS

PROJECT BRAYS Estimated Future Maps

Harris County Flood Warning System
Also shows historical information

FloodMap Mobile for iPhone (iOS)
More accurate, covers USA by address

FloodMap Mobile for Android

FloodMap Mobile for Windows Phone

(Use all of these with caution, when flood benchmarks change,
updates can be take time. Always verify with insurance company
and lender. The mobile APPS are generally excellent and
seem to be updated earlier in the process than the
Harris County tool.)