This article was originally published on Michael Bloom’s blog, Riparian Houston.
Tonight I received an email from Sanja Perica, Ph.D., Chief, Hydrometeorological Design Studies Center, Office of Water Prediction, National Weather Service, National Oceanic and Atmospheric Agency inviting me (and many others) to peer review a preliminary version of Volume 11, Version 1 of Atlas 14.
This preliminary volume is a wholesale update of statistically based rainfall intensity, duration, and frequency estimates for the state of Texas.
I’ve written about Atlas 14 four times before on this blog. Please check out these earlier posts if you need a primer.
In one of my earlier posts I estimated what the new depth of the 1% annual chance, 24-hour duration rain event might be. I did this by looking at a location in Louisiana that was a similar distance from the coast as Houston. The Louisiana Atlas 14 volume which had been completed earlier, so it was a good reference. In this older post I guessed that the updated 100-year event in Houston might be around 14 to 16 inches in 24-hours.
Well, drum roll please, now that the preliminary Atlas 14 numbers have been released for peer review we can see if I my guess was close. Take a look a the exhibit below.
My estimate was actually low. The 1% annual chance, 24-duration event in downtown Houston is now estimated to be between 16 and 17 inches.
A few notes about this figure:
- This figure is based on historic rainfall up to and including Harvey;
- These values should not be used for design purposes;
- Official floodplain maps have not yet been updated to reflect these new estimates;
- These values don’t reflect a pending NOAA analysis of potential climate change effects;
- The values in this figure might change as a result of peer review; and,
- Final, official numbers will not be released until May 2018.
If you’d like more information about the Atlas 14 project, come to the December 12, 2017 lunchtime panel discussion being hosted by the Houston Chapter of the Environmental & Water Resources Institute of the American Society of Civil Engineers.
If you’d like to comment on the preliminary data download it here. Send your comments to HDSC.Questions@noaa.gov. Comments are due January 19, 2018. Feel free to share this with others who may be interested.