This week the Texas Tribune, along with ProPublica, unleashed their second in-depth piece on Houston’s flooding risk. This one, entitled “Boomtown, Flood Town,” takes a closer look at the Tax Day flood event of last April and a broader look at Houston’s flood risk in the context of policy, development, and future climate change. It’s a long, thorough read, and I highly recommend the piece. This supplements their work earlier this year about our hurricane and storm surge risk. I personally think that is one of the more important articles that exists on Houston’s vulnerability to hurricanes.
In the “Boomtown, Flood Town” piece, a number of issues related to April’s flood event and Houston development are addressed. As I said, I encourage you to check it out yourself, but in the meantime, here are some key points that I’m taking away from this
Houston’s flooding issues are important because more people die in Houston from flooding than in any other city. No other urban area in America has flooded as much as Houston in the last 40 years.
“Boomtown, Flood Town,” from the Texas Tribune and ProPublica.
This post summarizes the historically wet period from the spring of 2015 through the summer of 2016 for the greater Houston area. Not only did the region set a record for total rainfall, it also experienced an astounding six significant rainfall events in just a little more than 12 months. Read on for a full analysis.
Based upon data from the National Weather Service, the 18-month period from March 1, 2015, through August 31, 2016, ranks as the wettest 18-month period on record for the city of Houston. In fact, the table below shows that each of the top-five wettest 18 month periods in Houston came during the last two years. Prior to 2015, Houston’s wettest consecutive 18 months had yielded a total of 106.68 inches. The March 1, 2015, through August 31, 2016 period annihilated that record by more than a foot of rain, with a total of 119.77 inches.
Here’s the data:
Wettest 18-month periods on record in Houston. (Paul Lewis/National Weather Service)
Nearly three months have come and gone since the Tax Day Floods ravaged the Houston area in April. As you may recall, during these storms rain fell at rates as high as 1 inch in just 5 minutes over parts of Harris County, with a maximum hourly rate of 4.7 inches. The rain topped out at 16.7 inches in just 12 hours over western Harris County. All told, Harris County averaged 7.75″ of rainfall for the event— equivalent to 240 billion gallons of water falling on the area.
One of the most memorable aspects of those floods came when both the Addicks and Barker Reservoirs filled up, and flooded the adjacent Highway 6. These watersheds located upstream of Houston provide flood damage reduction along Buffalo Bayou downstream of the reservoirs and through the center of the city.
A view of the flooded Addicks Reservoir. (John Chandler/Flickr)
The Harris County Flood Control District (HCFCD) has released their second report on the Tax Day Flood event last month. There isn’t anything shockingly new in this report, but it is an interesting read and brings the historic event into greater focus. I’ve scoured it and pulled a few interesting nuggets and images. (Note: For larger versions of the images just click on them.)
Large stretches of Western Harris County creeks and bayous saw 100 to 500 year flood levels exceeded. (HCFCD)
Note: This is the first in a series of reports by Matt Lanza that puts the Tax Day floods into perspective, and discusses what Houston should learn from this natural disaster.
On Monday afternoon the Harris County Flood Control District released its first official summary of the historic flooding that occurred last week in the greater region. I’ve read through it and compiled some highlights for here. (You can also view the report yourself in its entirety here). A serious thank you to Jeff Lindner at the flood control district who has worked tirelessly since last week to provide critical, useful, and interesting information to put this event into context and keep the region informed. He is also a must-follow on Twitter if you’re into weather, haven’t done so yet.
- Rainfall rates of 1″ in just 5 minutes were observed in Harris County. The maximum hourly rate was 4.7″. The maximum amount in 12 hours was 16.7″
- Harris County averaged 7.75″ of rainfall for the event. That’s equivalent to 240 billion gallons of water falling on the area. This exceeded Memorial Day (162 billion gallons) by almost 80 billion gallons of water. That event was more confined, whereas the Tax Day rains were much larger spatially.
Map of 12 hour rainfall totals. Click to enlarge. (HCFCD)