Nov. 12, 2019
But what about that orange plastic netting everywhere, the iron barriers and warning signs, the closed trails and sidewalks collapsing into the water, the white entrails of irrigation pipes hanging out of the dirt?
Buffalo Bayou Park between Allen Parkway and Memorial Drive is one of Houston’s great treasures, providing a rare experience of nature in the city, an opportunity to stroll and bike past fields of tall grasses and wildflowers, birds singing alongside the flowing stream. But what’s happening to the banks of the bayou there?
We sometimes get comments from people like, “Wow, Hurricane Harvey really chewed up the park,” referring to the historic August 2017 storm that flooded the Houston region.
But the fact is that the banks and sidewalks began collapsing in the park soon after the Harris County Flood Control District completed its $5 million “Natural Stable Channel Design” project in the park in 2015. (See also p. 33). Now the district is spending nearly $10 million to repair it.
The district’s Natural Stable Channel Design (NSCD) project began near the Sabine Bridge around 2010 and involved the removal of large amounts of native (and non-native) trees and vegetation, scraping and grading the banks, and altering the channel for more than two miles all the way upstream to the Shepherd Bridge.
Natural Channel Design or Natural Stable Channel Design, as the Flood Control District refers to its version of the controversial “stream restoration” methodology, was the basis for the Memorial Park Demonstration Project on Buffalo Bayou in Memorial Park. First proposed in 2010, that $12 million project, based on a flawed analysis of the type of bank collapse we have on Buffalo Bayou, met with popular opposition and fortunately was dropped by the Flood Control District after Harvey.
Natural Channel Design, widely used in government agencies, also has been widely criticized as unscientific, damaging, and prone to failure. The Harris County Flood Control District has a policy of using Natural Stable Channel Design wherever feasible (p.9), though the district did not use it in Terry Hershey Park in 2017, where it spent nearly $2 million to harden the north bank with massive concrete blocks.
The Buffalo Bayou Park Project
The $5 million-plus taxpayer-funded NSCD project downstream in Buffalo Bayou Park was part of the $58 million renovation and landscaping of the 160-acre park, led by the Buffalo Bayou Partnership, largely privately funded. SWA Group was the landscape design firm. The public annually provides some $2 million in maintenance and operating funds for the park through the Downtown Tax Increment Reinvestment Zone (TIRZ) #3.
Regularly described as “designed to flood,” the park, built in a floodway, was more or less completed just in time for “the wettest period in Houston history.” Since 2015, the concrete and asphalt sidewalks built into the lower banks, along with the concrete ponds in the dog park, have been repeatedly closed for lengthy repairs, with the large dog pond permanently filled in 2018, even after cracks had been sealed. The Partnership, which operates the public park through an agreement with the City of Houston, has spent some $3 million in private and public funds on flood-related repairs since the park was opened, including at least $400,000 in 2016 and $2.5 million following Harvey. This sum does not include the $3 million in federal funds the Flood Control District planned to spend in 2018 repairing trails and removing sediment.
Repairs Happening Now
In August 2019 the Flood Control District announced a $9.7 million federally-funded project to repair the banks in Buffalo Bayou Park. Described as part of its Hurricane Harvey Recovery Program, the project is intended to “stabilize the channel and prevent further erosion and damage to the channel.”
Many of the repairs are in the same locations that were repaired in 2015 and 2016.
The District was reluctant to describe to Save Buffalo Bayou the methods it planned to use for this project, which is funded by grants from the Natural Resources Conservation Service (NRCS) and the Federal Emergency Management Agency (FEMA). Representatives of the Flood Control District declined repeated requests for information, even at the urging of the constituent services coordinator for Harris County Judge Lina Hidalgo.
HCFCD Project Manager Jason Krahn finally responded by email on November 7 that the “bank repair material will consist of riprap and earthen fill.” District representatives declined to explain whether the District was using Natural Stable Channel Design for this extensive bank repair project, perhaps because this stretch of the bayou had already been “improved” with NSCD. Krahn did say that the “repairs will support the designed and constructed configuration” of the previous NSCD “channel conveyance restoration” done in 2012-14.
The contractor for the current seven-phase project, which began in August downstream near the Sabine Bridge, is James Construction Group, LLC. The previous contractor for the original NSCD project was Lecon. The current project is expected to take a year.
Why Is This Happening? Sidewalks Placed Where Banks Collapse Will Also Collapse.
Grading, scraping the banks, running heavy equipment over the banks and compacting the soil, removing trees and vegetation including buried fallen trees, mowing, installing irrigation, placing impervious concrete and asphalt sidewalks, even buildings, at the edge of the banks, even placing heavy chunks of concrete riprap on the bank: all these are well-documented ways of destabilizing the bank.
In addition, as we have often pointed out, the river has a memory and once straightened or altered, the stream will attempt to revert to its natural channel.
Not that the bayou banks wouldn’t slump or erode anyway. That’s what rivers naturally do, often repairing and reseeding themselves on their own if their banks haven’t been stripped of native riparian vegetation.
Sidewalks that are not placed where banks collapse will not need to be repaired.
What About That Big Sinkhole and Stormwater Outfall?
The floodplains of the bayou in the park have been plagued with sinkholes ever since bulldozing and landscaping began. A massive sinkhole opened up in 2015 underneath Allen Parkway near the intersection with Shepherd. This is the location of a City of Houston double-barreled (two 84-inch pipes) stormwater outfall draining Shepherd. The outfall, designed by Klotz Associates, was installed in 2014-15 near a buried tributary of the bayou. The bank, which had large trees removed to make way for heavy equipment, has been repaired several times since.
In the past year the sinkhole grew again, threatening the sidewalk and Allen Parkway, collapsing and damaging both of the stormwater pipes. The repair, recently completed, cost an estimated $1.2 million, according to a spokesperson for City Public Works.
What Are the Alternatives?
The Flood Control District has some useful ideas for softer, more reliable methods of stabilizing streambanks. In its Streambank Stabilization Handbook, the district recommends brush mattresses, branch packing, stakes of live trees, and more, although many of these methods, as described by the district, require deep disturbance and even compaction of the bank, with root wads absurdly sticking out into the stream. For bank protection and sediment control, public agencies across the country, even in Fort Worth, recommend leaving or installing large woody debris against the bank parallel to the stream, with the root wad facing upstream.
Other than that, the obvious choices would be to pull the sidewalks back from the edge, stop irrigating, and stop trying to repair the old meanders. Let the bayou repair itself, instead of assuming that engineers know better what the river wants to do.
It’s going to do what it wants to do anyway.