Flood Control Destroys Forest on Buffalo Bayou
May 6, 2019
(Updated May 7, 2019, with clarification from Harris County Flood Control. See below)
They’ve done it. Last week the Harris County Flood Control District began knocking down towering sycamores and pines in one of the last remaining forested areas open to the public on Buffalo Bayou.
This tree-cutting is not new. The Flood Control District has been razing forest next to streams all over the county for decades, mainly to excavate floodwater detention basins. Slowing down, holding back rainwater runoff is a good idea. But trees do that. And more. Flood Control is damaging the environment, destroying the limited access we have to nature in the city, while doing little to reduce flooding. Possibly even making it worse.
Their private consultants don’t consider the benefits of trees when they spend millions of taxpayer dollars on flood studies and plans. And there are significant benefits, including flood protection.
Because Leaving Trees in Place is Not a “Project”
The problem is, as the Federal Emergency Management Agency (FEMA) points out (see pp. 7-9), leaving trees in place—nature-based flood risk reduction—is not considered a “project.” There is a political bias in favor of costly, large-scale structural approaches, despite the obvious advantages to small-scale, non-structural, green or natural approaches to flood management. (Although in this case, they seem to be doing the project because it’s “cheap and easy.”)
“Protection of a natural channel and adjacent river corridor, floodplain or wetland often does not meet the conventional concept of a ‘project,’” notes FEMA.
The District needs “projects” in order to look like it’s doing something, especially after county voters approved $2.5 billion in bonds for flood reduction “projects.” And contractors don’t make money from not doing or not designing “projects.”
Other factors preventing more enlightened, more effective flood management include the lack of multidisciplinary expertise, leading to a dependency on old, traditional, and familiar engineering approaches, points out FEMA.
Like spending millions repairing the channelized banks of the bayou in Terry Hershey Park where the straightened stream is attempting to restore its natural meanders. Allowing the bayou to recover its bends, thus lengthening itself, would increase its capacity naturally and for free. (p. 11)
Because That’s What They Always Planned to Do
The trees recently downed by Flood Control were on the south bank of upper Buffalo Bayou in Terry Hershey Park, a semi-wild wooded area beloved by hikers and bikers. The 500-acre rolling linear park runs for some six miles on both sides of the bayou below Addicks and Barker dams in west Houston.
Flood Control, which owns the park, has been planning for years to level the trees on the south bank as they did in the Nineties on parts of the north bank. Popular opposition had stopped them. Until the flooding from Harvey.
Their plan is to create a series of shallow “detention basins” to slow down briefly a small amount of overflow from Buffalo Bayou when it floods. The $10 million project won’t stop anyone from flooding. The initial three basins, between Eldridge and Dairy Ashford, are said to be creating some 90 acre-feet of volume for the overflowing bayou to pass through next to its straightened channel. This is meant to compensate for additional stormwater that the City of Houston might drain into the bayou in the future.
Overflow Basins on the North Bank
The bayou in the park, before it was a park, had been stripped and straightened by the Corps of Engineers in the late Forties. This actually reduced the bayou’s capacity and led to increased flooding. In the Sixties the land was purchased by the Flood Control District. The trees grew back. But in the Nineties the District stripped most of the trees on the north bank of the park all the way to Beltway 8. There they excavated a series of shallow grass-lined basins between Dairy-Ashford and Wilcrest. These basins are advertised as capturing briefly some 100 acre-feet of overflow from Buffalo Bayou when it floods.
But there are no basins on the grassy, virtually shadeless north bank between Eldridge and Dairy Ashford. We asked Flood Control why, instead of destroying woods on the south bank, they didn’t put the new detention basins there on the opposite north bank where they’ve already cut down most of the trees. “I don’t have an answer for you other than we looked at the area,” said Matt Lopez, Precinct 3 Coordinator for the District. “The south bank was chosen because it had more appropriate space for what the design called for.”
Update May 7: Lopez clarified in a followup email that “Flood Control completed preliminary engineering that examined what impact this project would have to the environment and vegetation. The most feasible location for the start of the linear detention project after this review was the south side of Buffalo Bayou between Dairy Ashford and Eldridge.”
Lopez also offered a link to updated information about Flood Control plans for the linear detention basins.
A map of proposed detention basin sites issued by Flood Control in 2012 as part of its original Charting Buffalo study included new detention basins on the north bank between Dairy Ashford and Highway 6.
The park is named for environmentalist Terry Hershey, who in the Sixties helped save Buffalo Bayou from being stripped, straightened, and covered in concrete like Brays and White Oak bayous or lined with mowed grass like most of the streams Flood Control manages.
She would not be pleased.
A Narrow Strip of Trees
Flood Control does appear to be leaving a thin strip of trees and vegetation along the bank. They had promised something like ten feet. This sort of riparian buffer is crucial for holding the bank together, protecting against erosion, shading the stream, and helping to absorb and cleanse stormwater runoff. Even Flood Control tells us this. By contrast, removing the trees and vegetation and compacting the soil with heavy equipment, as Flood Control routinely does, reduces the ability of the land to absorb rain runoff and inhibits plant growth. (p. 14)
Unable to Change Course. Locked Into Doing the Same Thing
Knocking down trees does little to reduce flooding. But it does put a lot of taxpayer money into the pockets of private engineering companies, which appears to be the main function of the Flood Control District.
The District itself doesn’t actually cut down trees, mow the grass three times a year, or repeatedly dredge out the sediment washed into the stream because the stream had been stripped and dredged before. (Dredging, deepening and widening streams, by the way, only leads to more dredging and makes flooding worse.)
Nor does the District do any of its own engineering.
“The District obtains virtually all engineering design work for capital projects and maintenance repairs through consulting contracts and obtains all construction work through the competitive bidding process. All of the District’s routine maintenance (primarily mowing) is performed through contracts with private companies.” (p. 8)
So you can imagine the political pressure in favor of dredging, deepening, and widening, and against, say, leaving the trees and letting the grass grow. There’s a reason why commissioners’ court meetings are packed with engineers every week.
The District has an annual budget of $120 million, funded through a property tax rate of .02877 per $100, not including county bond or federal funds. (p. 13) More than half of the funds spent on Capital Improvement Projects in Harris County go to flood control projects. (p. 2)
It’s way past time for the District to start assessing and including the value and function of nature in its policies and practices and meeting its legal responsibility for the “conservation of forests.” (p. 1)