Historic Texas Floods and What Caused Them

June 14, 2017 by Marisa Keiser

Is Texas’ flood frequency due to over development and/or inadequate detention facilities? Or, is it because 100-year flood events occur more frequently than the statistical 100 years? Research indicates that it might be the latter. On average, the 100-year rainfall intensity in Texas is ±10 inches in 24 hours, but record rainfalls and floods are much greater than this.

Several floods in Texas can be attributed to Tropical Storms down pouring 30+ inches in a day or two, the occasional levee failure, and a 100-year event with ±10 inches in 24 hours or less.  A few examples include:

  • Parts of NW Harris County and Houston received up to 15 inches of rain in 24 hours, most of which occurred within 10 hours on April 18, 2016.
Tax Day Flood, April 18, 2016 at the intersection of Montrose Blvd. and Allen Pkwy adjacent to Buffalo Bayou in Houston, Texas. Photo: Brad Keiser
  • Tropical Storm Allison showered the City of Houston with 40 inches of rain on June 5th-10th, 2001.
    Tropical Storm Allison in Houston. Photo source: Houston Chronicle
  • The flood of 1949 in Fort Worth which received 11 inches of rain at Clear Fork of the Trinity River, resulting in levees breaking and spilling into the city.
1949 Flood at University Dr/7th street intersection with people in boats. Photo source: UT-Arlington

Though, levy failure can be improved with structural design and maintenance. What solution can we provide for hurricanes, tropical storms, large rain events, etc.?

Drainage requirements vary in the State of Texas, and not everyone is required to develop or improve conditions to the 100-year flood. For instance, while Austin and Dallas both require drainage systems to be designed to accommodate the 100-year storm, San Antonio’s regulations state that the 25-year event be sufficient for developments less than 100 acres, and Houston necessitates the bare minimum for newly developed areas, only designing for a 2-year rainfall event.

Is it time to rethink our drainage policies and design requirements?

Our team of civil, mechanical, structural and traffic engineers can help you plan your project, contact us today.

Written by Marisa Keiser

Marisa Keiser

Marisa Keiser is a graduate engineer in the Houston office of BIG RED DOG. Marisa graduated from the University of Texas at San Antonio in 2011 and join the BIG RED DOG team full time in June 2014. She is a rare, native born Austinite. Her professional experience has been focused on single family residential sites, including water quality and detention pond design, site investigation reports and due diligence investigations. Outside of work, she enjoys tutoring high school math, reading and traveling.