From the Flood Map Page on the Esri Web Site:
This map allows you to view continuously updated U.S. flooding information. You can see observed flooding locations as well as precipitation information.
The map also pulls in social media pertaining to flooding. In the Social Media box, you can change the search terms for YouTube, Twitter, and Flickr by hovering over the name of the feed, and then typing a new word into the displayed box.
Weather (Flood warnings, Observed Flooding, and Precipitation) updated every 15 minutes with NOAA data. A street map, satellite imagery, and a topographic map are available.