The Ny times featured Digital Globe images of the areas of Texas that were severely hit by Hurricane Harvey. There are also street level photographs to show the local spots before and after Harvey.
If you are interested in learning more about remote sensing from satellites the Applied Technology Institute (ATIcourses) has in-depth technical training programs.
The Washington Post has great images of the the rainfall rate relative to historic averages. The claim is that some Texas areas had a rainfall rate that is a 0.1% chance flood event in a year or 1 in 1000 in a year.
“A new analysis from the University of Wisconsin’s Space Science and
Engineering Center has determined that Harvey is a 1-in-1,000-year flood
event that has overwhelmed an enormous section of Southeast Texas
equivalent in size to New Jersey.”
Harvey released 40 inches to 45 inches of rain in a few days over areas of Texas or about 24.5 trillion gallons of water. Huge amount! – that is 3.5 ft in some areas.
The prediction of the frequency of strong flooding is tricky. The definitions and methods matter and can be slanted to make the author’s point. See the many comments to the above article.
By some measures this is the third 500 year flood in 3 years for Houston.
Please update this post with useful articles about the analysis of the Harvey rainfall and flooding in comparison to other major US flood events.