A Stormwater Project with Little Benefit and A Lot of Uncounted Cost
February 26, 2019
A large number of trees will be cleared in one of the city’s last remaining public forests on Buffalo Bayou because it’s the “easiest and cheapest” stormwater project to do, city and county flood control officials explain.
The trees are being removed to dig out shallow basins on the bank of upper Buffalo Bayou in Terry Hershey Park in west Houston, a rolling wooded area with paths used by hikers and bikers and wildlife. When the bayou overflows, the basins are meant to hold briefly a modest amount of water which then continues flowing downstream.
But the calculation of “cheapest and easiest” does not include future repair and maintenance costs where now there are none. A similar project on the once-forested opposite bank has required many millions of dollars in taxpayer funds for maintenance and repeat repairs to the bank in the decades since trees were cut.
Nor does this calculation include the additional flow into the bayou from the loss of trees and vegetation, which significantly slow and absorb rainfall and runoff. A study by the University of Arkansas reports that removing forest can increase runoff into streams by as much as four or five times. (p. 3)
It does not consider the financial value that the forest provides by cleansing the water and the air for free. Studies have shown that riparian vegetation is cheaper and more effective at cleansing our polluted water than even sewage treatment plants. A study of Houston’s urban forest by the US Department of Agriculture found that even including invasive trees, our modest tree cover captures carbon and other pollutants from the air worth hundreds of millions of dollars.
Also not included: the value of the mental and physical health benefit that trees provide to Houstonians, who suffer from a deficit of nature, many of whom were traumatized by the flooding from Harvey. Since ancient times wise people have known that the experience of even a small piece of nature has health benefits. (See also here.)
Nature is the Best Engineer
Making room for the bayou to overflow is a good thing, as is a focus on detention or “slowing the flow.” Cutting down trees and removing vegetation next to the bayou is not.
“Engineers have a hard time understanding,” says Bob Freitag, director of the Institute for Hazards Mitigation Planning and Research at the University of Washington and co-author of Floodplain Management, A New Approach for a New Era. “Trees aren’t in their model.
“We want trees,” says Freitag. “Trees do a lot of good things.”
There is a new field of engineering that understands and imitates the process of nature, melding engineering and biology and valuing ecosystem services, points out Freitag. “But those who do it are few and far between. It’s a pretty new field.”
No Reduction in Flooding
The planned detention basins next to the bayou channel do not even reduce flooding, despite a popular belief that they will. Officials confirm that the small basins will do nothing to reduce flooding downstream. “No, they’re not going to save people from flooding downstream,” said Matt Lopez, the Harris County Flood Control District’s Precinct 3 coordinator. “They’re not going to save folks from Harvey or any other storm.”
The purpose of destroying forest to dig out detention basins next to Buffalo Bayou in west Houston is to allow the City of Houston to drain more water from city streets into the bayou sometime in the future. This is the so-called “no-rise” requirement enforced by the Federal Emergency Management Agency (FEMA). To protect us from increased flood risk, FEMA requires that the City and everyone else prove that development within designated floodplains does not add to the flow in the bayou.
“We think there are advantages for the future when comes to drainage,” said Lopez.
Currently the City has no plans to drain more stormwater into the bayou, said Tommy Artz of the City of Houston Public Works Department’s Interagency Coordination Section. But the City has already paid $1 million to Flood Control to purchase some 30 acre-feet of the planned stormwater detention for future projects, said Artz
Some residents in neighborhoods near large commercial districts and Interstate 10 on the north side of the bayou are pushing for more drainage into the bayou. A representative of their neighborhood coalition declined to comment.
Artz explained that it was cheaper to purchase the detention from Flood Control than to buy land to build and maintain detention basins or install large underground culverts for temporarily holding stormwater. He described the purchase as a “bargain.”
Lopez explained that the flood control district already owns the land next to the bayou in Terry Hershey Park and has always planned to use it for flood management projects.
He said he believed that the agency planned to try to leave trees on the banks. “Trees help us prevent erosion,” he said.
Flood Control is planning three initial basins on the south bank of the bayou between North Eldridge Parkway and Dairy Ashford Road. Construction is to begin within weeks. The basins will briefly hold about 90 acre-feet of overflow from the bayou when it floods before allowing it to drain back into the bayou.
The district has already spent millions on the south bank linear detention basin project in the past decade, including paying various engineering firms for vegetation surveys and design. Lecon, Inc. has the $1.8 million contract to construct the initial three basins.
Decimation of Our Urban Forests
The tree removal project comes at a time when Houston’s remaining urban forests are being decimated. Hundreds of trees have already been felled in Memorial Park, our once-great public forest in the middle of the city, as part of a $200-300 million landscape plan for the park. Hundreds more, including towering pines, are already tagged for removal to make way for an artificial land bridge over Memorial Drive. More trees are being felled for the $13.5 million remake of the park’s popular public golf course into a professional tournament course, the plans for which city officials refuse to reveal. And then there are the numerous big trees that will be cleared in order to plant a monoculture of young pines in rigid rows on the west side of the park – a planned memorial to those who died in World War I. Planting a single species of trees in regimented rows, however, is a prime example of the wrong thing to do in the midst of an alarming loss of the biodiversity that supports life. Also it’s ugly and unnatural.
Years ago the Harris County Flood Control District, in collaboration with the Buffalo Bayou Partnership, stripped trees and scraped vegetation from the banks of Buffalo Bayou in Buffalo Bayou Park downstream from the Shepherd Bridge. The result has been a disaster, with continuous costly repairs to collapsing banks and sidewalks.
The flood control district continues its decades-long practice of cutting and bulldozing trees on streams, oftentimes merely to provide access for bulldozers and other heavy equipment to the bank. Most recently, for example, Save Buffalo Bayou documented piles of large trees felled by the district’s contractor along Langham Creek in Addicks Reservoir. (See photo below.)
The district is legally responsible for the “conservation of forests” according to its 1937 founding charter. (P. 1)
In the wake of Hurricane Harvey, the Harris County Flood Control District revived a controversial plan to capture flow out of the bayou with a series of shallow basins on the forested south bank of the stream in Terry Hershey Park. Residents, conservationists, and others, banding together as Save Our Forest, have been fighting to preserve the trees on the south bank since at least 2010. However, many of those forest activists were among the thousands who flooded on upper Buffalo Bayou during Harvey. With homes destroyed and health damaged, their ability to oppose the project has been weakened.
“I feel like they are pushing this thing now when they know people are too distracted to resist them,” said one distraught resident.
Terry Hershey Park, run by Harris County Precinct 3, occupies about 500 acres of land along some six miles of bayou that the district purchased from the federal government in the Sixties. The federal government had stripped, straightened, and shortened the bayou there below the two federal flood control dams, Addicks and Barker, during the late Forties. Straightening—channelizing—the bayou essentially reduced its capacity, rendering future residents more vulnerable to flooding, besides damaging its essential functions. Channelizing streams for reducing flood risk has been largely abandoned by the federal government and agencies elsewhere because it actually increases flooding, among other problems.
Modern stormwater management emphasizes stopping, slowing, and absorbing stormwater before it floods a stream, not after. (See Freitag, et al.)
Allow Bayou to Increase Capacity Naturally and For Free
The straightened bayou in Terry Hershey Park, like all rivers and streams, continues to try to restore its natural bends or meanders and recover its former length and capacity. Allowing it to do so would in fact probably be the easiest and cheapest stormwater management project. Restoring meanders to channelized streams is modern practice. “Restoring meanders to rivers that have been straightened … increases the in-stream storage capacity and slows the downstream propagation of the flood peak, thereby decreasing downstream flood risk …,” reports the nonprofit International Rivers. (p. 11)
The park is named for legendary environmentalist Terry Hershey, who in the Sixties and Seventies organized landowners, conservationists, garden club members, and influential politicians, among many others, to protect Buffalo Bayou from being stripped, straightened, and covered in concrete.
Learn more about Houston and trees from the City of Houston’s Office of Sustainability.
What to do: Contact Harris County Precinct Three Commissioner Steve Radack. He’s in charge.