How Big Pipes Block the Flow in Our Streams During Storms
Jan. 17, 2022
In a city full of engineers, surely they would get the engineering right.
But somehow the banks of our bayous and streams are punctured with stormwater drainage pipes that block the flow during storms. Pointing directly across the stream, they shoot a powerful force of rainwater runoff against high flow in the channel. This acts like a dam, stopping our streams from draining, causing water to back up as much as a quarter mile, according to witnesses. It also creates damaging turbulence and erosion and increases flooding.
It’s not like we don’t have a problem with flooding. Authorities are proposing multi-billion-dollar fixes to move more stormwater faster through the pipes and streams that collect rainwater from our roofs and streets and parking lots and send it out to Galveston Bay. These are big fixes like dredging, deepening, and widening 22 miles of Buffalo Bayou from the federal dams in west Houston to downtown. (p. 111) Or building a massive flood tunnel from the dams to the bay. (p. 106) (See also here and here.)
Seems like they might fix the problem drainage pipes first.
Violating City, County, and Federal Regulations
Anything greater than a 60-degree angle to the bank is a violation of those regulations. (See Houston Public Works, Infrastructure Design Manual 2021, pp. 181, 183 and HCFCD Policy, Criteria, Procedure Manual, p. 230.) Actually, the federal requirements are even stricter. The Corps of Engineers requires the Harris County Flood Control District (and thus the City of Houston) to adhere to outfall angles no greater than 45 degrees to the bank. (Regional General Permit SWG-2009-00123, p. 3) The City of Austin, among other places, also requires an angle of 45 degrees or less. (See G.)
These regulations are at least twenty years old, if not older, according to representatives of Houston Public Works.
So how did we get all those stormwater outfalls blocking the flow in the bayous?
An Old Story
We’ve been pointing out this problem for some time. There’s the massive stormwater outfall in Memorial Park’s Old Archery Range, site of the public boat launch west of Loop 610. It was built in 2012-2013, designed by the engineering firm AECOM to point directly at the opposite bank, despite the outfall angle regulations.