Myth: The bank erosion that is occurring on a portion of Buffalo Bayou is a normal process of natural streams.
The forces that are driving bank erosion and sediment deposition on this part of Buffalo Bayou greatly exceed those that originally shaped the channel, prior to the urban development of west Houston. The rapid runoff of stormwater due to the presence of multiple water-shedding surfaces, combined with the prolonged releases of water from two upstream reservoirs, have caused the bayou’s formerly stable channel to widen and to cut away at the bases of vulnerable banks, leading to collapse. The high rate of erosion on this part of Buffalo Bayou (359 tons per year*) is also increasing the deposition of sediment into areas where the flow of water is slow. The goal of the Memorial Park Demonstration Project is to work in concert with the bayou’s natural forces, making necessary adjustments to the channel to allow it to dissipate the energy of the flowing water while avoiding destructive widening. This is the essence of Natural Channel Design: letting the stream reach a new state of dynamic equilibrium and natural stability in the face of urban change. Without this attention to the bayou’s overall form, its riparian vegetation will be continually stressed and left without a foothold to naturally protect the streambanks. The project will also benefit ongoing efforts to address the bayou’s high levels of bacteria, which can adhere to and grow on sediment particles.
Myth: Bulldozers will strip Buffalo Bayou of woody vegetation.
Unavoidably, heavy equipment must be used to reshape portions of the bayou to address the problems of erosion and deposition. Soil that is removed will be stored and then returned as part of the re-vegetation process using diverse native plants (trees, shrubs, forbs, and grasses) that are well-suited to the stabilization of riparian areas. (A riparian area or riparian zone is the interface between upland regions and a river or stream.) Over time, the vegetation will form a nearly closed canopy over Buffalo Bayou, much as it did prior to urban development of the Buffalo Bayou watershed and the construction of the Addicks and Barker reservoirs. BPA will closely monitor the re-vegetation process to ensure it meets the project’s goals and design criteria.
Myth: The Harris County Flood Control District calls the plan a “demonstration project” because the county intends to use this disputed, heavy-handed method on the natural landscape of Buffalo Bayou in neighborhoods upstream.
The project is intended to demonstrate to private landowners along Buffalo Bayou and other natural waterways in the region that by applying a collaborative, holistic approach to stream restoration, significant benefits to the stream, riparian habitat, and water quality can be realized. In contrast, the “patch-in-place” armoring and the spot repairs done by individual landowners along the bayou are leading to increased degradation of the bayou and a loss of crucial habitat.
The Harris County Flood Control District currently has no plans to apply this design methodology to other parts of Buffalo Bayou. Following construction of the project, its success will be thoroughly evaluated, with an eye to assessing applicability of Natural Channel Design concepts to maintenance practices in highly erosive areas along other bayous in Harris County.
Myth: Opponents to the project describe the plan as "pseudo-science".
The channel evaluation and restoration methodology developed by hydrologist Dave Rosgen, Ph.D., is well established in the scientific literature, and it is increasingly employed by the civil engineering community (see link below for “Entering the Mainstream” in the August 2010 issue of Civil Engineering). It has been adopted by the U. S. Environmental Protection Agency and the U. S. Army Corps of Engineers as a preferred design approach.
- River Restoration Using A Geomorphic Approach For Natural Channel Design by David L. Rosgen, Hydrologist/Geomorphologist
- Entering the Mainstream by Jay Landers
- Physical Stream Assessment: A Review of Selected Protocols for Use in the Clean Water Act Section 404 Program - US Army Corp of Engineers