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.
There are all those big pipes aimed at the opposite bank in Terry Hershey Park, property of Harris County Flood Control, just below the dams far out west. (Homes along that straightened stretch of the bayou flooded badly when the Corps was forced to open the floodgates of the overburdened dams during Harvey.)
Closer to downtown the bayou is lined with outfalls old and new, large and small, that aim at the opposite bank in Buffalo Bayou Park. Harris County Flood Control has had several opportunities to realign some of those pipes, most recently while stripping and grading the bayou banks during its $10 million project in 2020 to “repair” the “natural stable channel design” work the district had just recently completed. (See also here.)
This doesn’t even include the dozens of big pipes blocking the flow on Brays and other bayous.
Previously when we asked Harris County Flood Control about the rule-breaking right-angle pipes in those parks, the answer was always “those are not our pipes.”
Whose Pipes? What Pipes?
But a few weeks ago we started receiving inquiries and complaints about trees removed and bulldozing of the bayou bank south of Memorial Drive, just upstream of the Shepherd Bridge. It turned out that the City was installing a massive new outfall. And it was pointing directly across the stream.
So we wrote to the director of Public Works, Carol Haddock, pointing out the numerous existing violations, and asked why the City was now installing a big new pipe that violated City regulations and was going to cause problems. We received an informative response from Lagnesh Varshney, the City’s managing engineer for drainage and transportation operations.
He generously explained some technical details. Angling the new replacement pipe more downstream to conform to regulations would require a new manhole, disrupting traffic and impacting the pavement on Memorial Drive. It would also take more land, requiring more trees to be removed. In addition, he wrote, pointing the new replacement outfall more downstream would conflict with another outfall close by.
Okay. But what about all those pipes and outfalls in the park below Shepherd Drive where flood control had just stripped and bulldozed the bank anyway?
Varshney replied that his department was only responsible for outfalls that were damaged and in need of repair or replacement. He suggested we ask the Harris County Flood Control District about those drainpipes sticking out like cannons pointing at the opposite bank.
We have sent another inquiry to the bosses at flood control.
A flood control spokesperson says they are looking into it and will have answers in a week or so.
In the meantime, we were curious about those relatively new outfalls at Woodway in Memorial Park and in Buffalo Bayou Park pointing at the opposite bank. How did they manage to get approved by the City? In Buffalo Bayou Park one outfall, which replaced a natural tributary, took out the sidewalk on the opposite bank during Harvey. (See images above.)
Varshney said the city was looking into that.