Editor’s Note 2020: The Harris County Flood Control District dropped the Memorial Park Demonstration Project after Hurricane Harvey in 2017. However, these issues and answers are still useful. The River Oaks Country Club, which owns the south bank of the bayou opposite Memorial Park, has since destroyed the relatively natural bank in three areas, razing trees, bulldozing, and installing sheet pile and concrete walls. The flood control district has had to completely replace its Natural Stable Channel Design project in Buffalo Bayou Park between the Shepherd and Sabine bridges. The district, in pursuit of outdated flood management policies, continues to raze trees and destroy the few remaining forested streams in the region.
1. The Memorial Park Demonstration Project will stop erosion of terribly eroding banks.
Answer: The existing riparian forest is the best way to control erosion. And this historic stretch of Buffalo Bayou as it flows between Memorial Park and the River Oaks Country Club is some of the healthiest, most beautiful, most stable bayou that we have left. The Harris County Flood Control District found, in a study presented in December 2013, that the mean annual bank erosion rate in the project area was less than half an inch.
In places, especially following rare large storms and very high waters that overflow and saturate the banks, such as the Memorial Day storm of 2015, the faces of high banks have slumped or rotated away vertically, often carrying trees and vegetation to the bottom, creating the characteristic steep, concave look of our bayou banks. In fact, the photo above shows at the water’s edge the layer of hard red Beaumont clay that serves as the glide plane for the saturated sediment as it slides out of the bank. Some of the sediment falls into the stream, but most of it remains at the bottom, forming terraces, and trees and vegetation continue to grow. This can also happen because of uncontrolled runoff or heavy irrigation at the top, especially when stabilizing trees and vegetation have been removed (think mowed golf course and landscaped yards).
The engineering consultants for the flood control district have misdiagnosed the type of erosion that is happening in this stretch of Buffalo Bayou. As a result the project, as described in the permit application, focuses mistakenly on shear stress or lateral erosion caused by the water flowing downstream rather than the vertical instability that produces slumping. The methods proposed for this project will do nothing for vertical instability. In fact, the proposed structures — root wads, etc., — will likely slide away, as they have washed away in other areas. The proposed project will fail. Much of the sandy sediment that appears in dunes on the banks or even in the channel following high flows is actually sediment in transit, entering the reach from upstream, soon to flow away again, according to our scientific experts. But this temporary buildup of sediment is often mistaken for failing banks in the project area.
2. The project will improve water quality.
Answer: The permit application from the Harris County Flood Control District to the Army Corps of Engineers makes clear that this project will not improve water quality. Bacteria and sediment mostly come from pollution and uncontrolled runoff upstream. Sediment contributed from this area will likely increase due to construction and the removal of vegetation from the banks. Removal of trees, plants, and the living soil from the banks will destroy the bayou’s natural ability to improve water quality.
3. The project will stop bacteria-laden sediment from ending up on the sidewalks of the newly landscaped Buffalo Bayou Park east of Shepherd and in the ship channel.
Answer: The amount of sediment contributed by these natural banks is miniscule, about 276 cubic yards per year, according to the permit application. But the project itself will likely increase the amount of sand and silt on the sidewalks in the still unfinished downtown park and may also increase the amount of bacteria, since among other things the project will dig up and kill the soil’s natural ability to fight bad bacteria. (Update Dec. 21, 2015: Buffalo Bayou Park is now finished, if that can ever be truly said, since the banks and landscaping were already collapsing and eroding before they were done. The banks of that popular and much-needed park were supposed to be more stable, an example of flood control’s Natural Stable Channel Design and the model for what flood control, the Bayou Preservation Association, and that park’s landscape designer SWA Group wanted to do upstream in Memorial Park. Buffalo Bayou Park is an expensive and tragic failure.) (See also here: Endless Repairs.)
In addition, the project will increase the volume and velocity of the water passing through the channel, which will further damage property downstream, especially those already-eroding areas where vegetation has been scraped such as Buffalo Bayou Park. A 1995 study of Buffalo Bayou by Brown and Root found that “the channelization of the segment … that flows through a densely developed part of the City caused faster runoff, increased flow velocity, and increased sedimentation.”
4. The bayou is a patchwork of various erosion control methods, and this project will demonstrate to property owners on the bayou the best way to control erosion.
The project is demonstrating to property owners exactly the wrong thing to do to prevent erosion. Property owners have problems with erosion of their riverfront land when they remove the trees and plants for views and dig up the soil for landscaping. These trees and plants hold the banks together, and preservation of the specially adapted vegetation and soil on waterways, known as a riparian zone, is a goal of virtually every state and federal agency charged with protection of our clean water, waterways, and wildlife habitat.
5. The riparian forest in Memorial Park is not natural, not old, doesn’t exist, and/or is filled with invasive species. The Memorial Park Conservancy and the Bayou Preservation Association say the bayou here has been “altered.”
The survey conducted by the flood control district rated the riparian forest in the project area as nearly perfect—about what you’d expect in a natural area largely undisturbed. Some of the trees here may be 80 to 100 years old or more. Proponents of the project are deliberately misleading the public when they claim, as the Memorial Park Conservancy does in its March 9, 2015, final presentation of a proposed Master Plan for Memorial Park, that the bayou flowing past the park has been “altered.” This part of the bayou has never been channelized or dug up or filled in. Those who should be protecting our bayou are arguing that because the bayou has naturally adjusted and adapted to increased flows from urbanization, it’s not natural and therefore we need to destroy it all. They also exaggerate the amount of invasive trees and vegetation on the banks of the bayou. In any case, the presence of invasive species is not a reason for bulldozing and destroying the bayou’s entire ecosystem.
6. Those high, steep bluffs along the bayou here are scientific evidence that the bayou is trying to change course. They are the result of recent erosion. They are a big erosion problem.
Answer: Those magnificent high, vertical bluffs in the Hogg Bird Sanctuary and in Memorial Park are long-lived features of our prairie landscape and should be respected and preserved as part of the historic natural landscape of this remarkable area. They have little changed in at least the last hundred years. Serving as “bumpers” to the running river, holding the bayou in place, they are remnants of Pleistocene landforms hundreds of thousands of years old that control the course of all the west-east running streams in the Houston area (upper Spring Creek, Cypress Creek, Buffalo Bayou, Clear Creek, Brays Bayou, Sims Bayou). Aerial photographs from 1930-2010 show that the *least* migration of the bayou channel occurs where the banks are the steepest.
7. Trees fall into the bayou.
Answer: Trees falling into the bayou are part of the natural and necessary cycle of a healthy, functioning river system. Fallen trees help slow storm waters, trap sediment, fortify the banks, and provide fish and wildlife habitat.
8. The bayou is whipping all over the place, trying to change course.
Answer: The course of this 18,000-year-old river has little changed within recorded history. Even the shifting back and forth of a meander at the eastern edge the park has remained within a defined, flat area. But rivers move. It’s natural. And here the bayou has room to move. We should let it. Dynamic rivers are more biologically diverse.
9. The method being used to “stabilize” and “restore” the bayou is scientifically proven and successful.
Answer: The controversial method being used in this project and several other projects in the county, including in Buffalo Bayou Park downtown, is neither scientific, proven, nor successful. So-called Natural Stable Channel Design is based on a method invented by Dave Rosgen, whom the scientific community considers a charlatan. His widely used and highly destructive methods have no scientific basis or monitoring, do not conform to scientific practice, and offer no evidence of erosion control or reduction. They have a high rate of failure, which leaves us with the nightmarish possibility that after destroying our beautiful bayou, the reconstructed, denuded channel could wash out, leaving us with a wasteland.
10. It’s better than using concrete.
Answer: Is that a good reason? It’s basically the same ugly, misguided channelization, but without the concrete and with some curves.
11. It will all grow back. The wildlife will return. It will be better than before.
Answer: There is no scientific evidence for these claims. They are taking a natural bayou and riparian ecosystem and turning it into a lifeless, landscaped ditch. Even if the bayou doesn’t wipe it out, it will never be the same. (They don’t want it to be the same, else they wouldn’t be wiping it out in the first place.) It would take fifty to hundred years for a completely planted forest to grow back in this area, if ever. This is some of the last, closest thing to wilderness we have in the middle of our city. We need to honor and protect this historic nature area.