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.”