As more settlements in Texas and France are impacted by severe flooding, this is a good time to thank the hydrologists at the NOAA who forecast river level rises in advance and give residents in affected areas time to move to higher ground. Along with topgraphic, rainfall, and weather data, monitoring stations maintained by NOAA and the USGS along rivers provide critical real-time information about river levels. NOAA scientists access this data using the dataRetrieval package for R, which they then incorporate into flood prediction models and use to generate animations like this one of the flood of the Delaware in February this year:
According to the AdventuresInData blog, which posted the above animation (creating using R's animation package):
The plot shows the discharge per drainage area (cfs/square mile) responding to rainfall. Tributaries cause unequal response initially, but then the entire system settles into a flow wave rolling downstream.
Note that "river miles" measures from the river's mouth, so the flood surge moves from right to left in the animation. More details at the link below.
AdventuresInData: Animated Flow in the non-tidal Delaware River