Is that A Good Idea?
The Value of Lost Ecosystem Services
April 29, 2025
Digging out the land to create basins to hold stormwater and prevent flooding is a good thing. But is cutting down forests of trees a good way to do it?
A study commissioned by Save Buffalo Bayou has found that removing forests to dig out stormwater basins results in the significant loss of vital ecosystem services.
Trees, especially a forest of old trees, provide numerous benefits. In addition to slowing and reducing stormwater on their own, protecting and stabilizing streambanks, trees and plants help cleanse and cool the air, provide habitat and help sustain biodiversity, and help us maintain our mental, physical, and emotional health, among many other things, like nourishing the water table, preventing subsidence, and more.
For years now the Harris County Flood Control District has been clearing hundreds of acres of forests alongside streams to create detention basins. These types of basins are generally designed to temporarily divert water from flowing streams, as opposed to upland basins that collect rainwater running over the land.
Of course, the district was created in 1937 to help the US Army Corps of Engineers strip, straighten, and encase in concrete our then-forested rivers and streams. (See Brays Bayou and White Oak Bayou, for instance, both formerly wooded and winding.) But that project was stopped in the early 70s, initially by environmentalists. It is now generally accepted that stripping and channelizing streams to make water flow faster only increases flooding. Slowing the flow is the way to go. Stop the runoff before it floods the stream. (See also here.)
It might come as a surprise that Harris County has so much forest. Though largely coastal prairie, historically the many streams, creeks, and rivers that wind through the county towards the gulf have been lined with magnificent forests of oaks, pines, sycamores, cottonwoods, and more. They are called riparian forests.
It might also come as a surprise that the Harris County Flood Control District, in its founding charter, was tasked with the seemingly contradictory responsibility for the “conservation of forests.” (p. 1, section 1) Unfortunately, the county has lost some 10 percent of its tree canopy between 2011 and 2021, according to recent report from Rice University’s Kinder Institute.
The world is losing its forests, a cause for global concern. But what is the local impact of removing forest in our own part of the world? And is there a better approach to reducing floodwaters?
Save Buffalo Bayou, with the help of the Jacob and Terese Hershey Foundation, commissioned a study to evaluate the loss of ecosystem services from deforestation, including removal of the soil. The study looked at four detention basin sites from a variety of watersheds and landscape contexts: Clear Creek in southeast Harris County, Cypress Creek in northwest Harris County, and two on Halls Bayou north of Houston.
To quantify the value of ecosystem services contributed by each of these sites before and after excavation, the study used the Ecosystem Services Valuation Tool developed by Earth Economics and the Land Trust Alliance. (p. 12)
The study also looked at the water storage capacity of the top five-foot layer of soil prior to removal at each site.
Results
In addition to the significant loss of ecosystem services valued in the millions of dollars annually, the study explains that living topsoil can take centuries to form (p. 20) and that removing that soil exposes dense, deficient, salty, crusty, even toxic soil that can limit plant growth. (p. 24)
The study points out that while excavated basins do indeed store more stormwater than the unexcavated soil alone would hold, the forest soil can hold a surprising amount of stormwater, which also nourishes groundwater, serving the vital function of replenishing streams and preventing subsidence. (p. 23)
The ecosystem services evaluated included air and water quality, climate stability (carbon storage), provision of wildlife habitat, recreation, and aesthetic value. (p. 12)
The four sites were A521-01, a 58-acre project on Clear Creek in southeast Harris County; K500-05, a 16-acre project on Cypress Creek in northwest Harris County; P518-03, 41 acres and P518-04, 83 acres, both on Halls Bayou north of Houston. (p. 5)
Losses in the Millions
The study, titled “Stumped,” found that the Clear Creek site (A521-01) lost half of the annual value of its ecosystem services, dropping from its pre-excavation value of $5,107,080 to $2,545,358. The Cypress Creek site (K500-05) lost a staggering three-quarters of its annual value, dropping from $2,841,370 to $764,730. Even worse, the two sites on Hall’s Bayou (P518-03 and P518-04) dropped 85-95 percent in annual value, from $5,571,812 and $9,387,560 respectively to $825,266 and $595,312. (p. 15)
Conclusions: Avoid Riparian Areas
The study, which was performed anonymously by a professional hydrologist, notes that in prior years, local flood control district detention basins were usually built away from forested streams, in upland areas. The recommendation, in addition to saving and using the valuable soil removed, is to avoid riparian areas and “locate detention basins in upland, historically non-woodland areas … better located to accommodate runoff before it gets to stream channels.” (p. 26)
Read the entire study, “Stumped.”
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