FloodMap Mobile is available for iOS, Android, and Windows Phone. It shows all the FEMA floodplains, USGS gages, National Bridge Inventory, and a lot more. The app will show you the floodplains on a map and your current position so you know what to expect. Great for public users because it's hard to visualize a floodplain and you aren't going to have paper flood maps of the city with you - but in FloodMap Mobile all the FEMA floodplains and your current GPS position can be in your pocket. It will also give USGS ground elevation, flood insurance costs, past flood disaster payouts, and other reports about flood loss.