The greater Houston area has over 2,500 miles of waterways. Of these, 800 miles are natural stream beds; six percent is channelized. Two of the major bayous in this system are Buffalo Bayou, which remains unchannelized, and Brays Bayou, of which a portion has been channelized.

Our bayous are under constant pressure from increased development. In addition, bayous have to function on multiple levels. They must accept stormwater and remove it quickly without flooding nearby residences. They must provide habitat for fish, birds. and other animals. They are also expected to provide recreation for hikers, bikers, and canoe enthusiasts.

Water quality in the bayous is dependent upon the efficiency of our wastewater treatment plants and the nature of stormwater runoff. One of our most natural bayous, Buffalo Bayou, is providing poor to moderate habitat for our fish and benthic macroinvertebrate life. Concrete-lined bayous are also providing very poor habitat.

I. Buffalo Bayou
Buffalo Bayou’s watershed covers 101 square miles and is the sole outlet for Addicks and Barker reservoirs. Buffalo Bayou empties into the Houston Ship Channel after combining with White Oak Bayou and flowing through downtown Houston. The watershed is almost entirely developed in its lower reaches and mostly undeveloped in the upper reaches.

The Army Corps of Engineers (COE) enlarged and straightened the upper reaches of the Buffalo Bayou channel near the outlets of Addicks and Barker dam in the 1940s. A 1935 storm had caused Buffalo Bayou to rage through downtown Houston 46 feet above normal, damaging 25 blocks of the central business district and 100 blocks of a highly developed residential area. The flood also killed seven citizens. In response to the disaster, Houston business leaders asked for federal assistance in solving the city’s flooding problem.

Harris County Flood Control District (HCFCD) was formed by the Texas Legislature in 1937 to sponsor federal projects in the county. The Corp of Engineers in 1937 recommended a major flood control project for Buffalo Bayou including the Addicks and Barker reservoirs. In 1963, the COE proposed the rectification of Buffalo Bayou, including concrete lining of the channel, but a group of concerned citizens went to then-US Representative George H. Bush and convinced him to stop the project. That group later named themselves the Bayou Preservation Association.

Strong and effective community resistance to channelization of Buffalo Bayou has limited the flow that the bayou can carry, and steep slopes have led to severe erosion problems. However, since the building of the reservoirs, out-of-bank flooding is not very common. An exception occurred in 1992 when rainfall approximately equal to the so-called 10-year flood repeatedly flooded 77 homes. (Computer models predict a 10-year flood will affect three square miles or approximately three percent of the watershed. A 100-year flood will affect six square miles or six percent of the watershed.) The current plan for the watershed includes detention and channel work on the tributaries and some limited clearing and buyout, as well as geomorphological improvements along the main channel.

Development within the lower watershed prohibits the construction of traditional detention facilities. However, it is estimated that employing linear detention techniques along the bayou will lower 100-year flood elevations by as much as 2.5 feet. Areas of the lower watershed will be excavated down to a level above the normal high-water elevation, corresponding with the maximum releases from the dams at 2,000 cubic feet per minute. This will result in a loss of habitat, but a replanting of these areas with a mix of native trees and understory should reestablish habitat and restore the lower bayou’s recreational value.

A proposal to divert stormwater to a large storm drain under the I-10/Katy Freeway corridor has also been discussed as a way to prevent flooding along Buffalo Bayou.

II. Brays Bayou
Brays Bayou has a drainage area of 128 square miles. The main channel within the watershed extends 31 miles from the headwaters in east Fort Bend County to the mouth of the Houston Ship Channel. The region is highly urbanized with about 85 percent of the watershed being developed. The lower 25.4 miles was channelized and lined with concrete in the 1960s by the COE. Even so, storms over the last two decades have flooded several hundred structures. In response to this flooding, HCFCD has partnered with the COE to plan, design, and construct the Brays Bayou Federal Project.

The Project includes an upstream element and a downstream element. The upstream element involves the excavation of three stormwater detention basins and channel modifications that include 3.7 miles of concrete lining. The three basins, when completed, will provide approximately 8,100 acre-feet of stormwater storage for a cost of $195 million. Strong community opposition to channelization has been voiced.

The downstream element of the project includes the enlargement of the current channel from the mouth of the Houston Ship Channel upstream to Fondren Road. The widening will occur on one or sometimes both sides of the bayou. Much of the lower portion of the bayou is concrete lined, and in this area widening will be above the lining.

A second feature of the downstream plan includes a large detention basin along Willow Waterhole, a tributary to Brays Bayou. The area is approximately 200 acres. A third feature includes the replacement of thirteen bridges that span Brays Bayou.

The downstream element will cost $229 million and will reduce water elevations from a 100-year flood from 0 to 3.0 feet depending on location. Overall, approximately 14,500 homes will no longer be in the floodplain of the 100-year flood.

Water Quality
During periods of low flow, Buffalo Bayou and Brays Bayou are almost 100 percent treated wastewater effluent. The City of Houston, Harris County, and the Texas Natural Resource Conservation Commission (TNRCC) sample the bayous in the Houston area several times per month. Sampling parameters include temperature, dissolved oxygen, pH, chloride, sulfate, ammonia nitrogen, nitrate, nitrite, ortho phosphorous, total phosphorous, fecal coliform, and metals.

In January 1998, the TNRCC released its draft list of impaired waters. Buffalo Bayou tidal was listed for exceeding the state screening level for fecal coliform and the nonsupport of intermediate aquatic life due to excessive copper. Buffalo Bayou above tidal also exceeded the screening level for fecal coliform.

Brays Bayou was not evaluated separately for water quality compliance by the TNRCC. A trend analysis of water quality in Houston’s bayous was completed in March 2000 for the Houston-Galveston Area Council. Results of that analysis identified the following concerns:

1. Brays Bayou at South Main Street (lower portion of the bayou, concrete lined) exceeded the lead stream standard of 5 ug/l seven times between February 1993 and August 1997.
2. Buffalo Bayou tidal samples for fecal coliform showed all values above the screening level of 200 cfu/100 ml.
3. Copper and mercury were also identified in lower Buffalo Bayou as a water quality concern that requires continued monitoring.

In 1998, Harris County, the City of Houston, the Texas Department of Transportation, and HCFCD began sampling stormwater runoff three times a year. Although there are presently no discharge standards, samplings in 1998 and 1999 were worrisome: The stormwater data show nutrients, for better or for worse, to be in range with urban runoff nationally, but fecal coliform counts exceed screening levels.

Habitat
The US Geological Survey (USGS) completed a study of habitat in Houston’s bayous in 1997 and 1998. The objective was to evaluate in-stream biological resources at above-tidal stream sites throughout the region. The study looked at fish, benthic macroinvertebrate, and stream habitat data. Four sites along Buffalo Bayou were evaluated. No sites on Brays Bayou were tested; however, one channelized site on White Oak Bayou was evaluated.

Benthic integrity and habitat integrity scores were summed to give a total integrity score. Of 31 sites evaluated for total integrity, the highest score was 34 and lowest score was 9. Buffalo Bayou downtown had the poorest integrity score of all streams evaluated. This area of the bayous has little habitat left and receives the stormwater runoff from Houston’s downtown buildings.

White Oak Bayou had a slightly higher score of 13. This site is concrete lined. Buffalo Bayou at Eldridge Parkway had a total integrity score of 25.

Some important conclusions from the study: Reaches with a large percentage of forested upstream drainage generally have a more meandering channel and higher total integrity score. Reaches with a larger percentage of urban and agricultural drainage have a lower integrity score. Population per square mile is a good predictor of stream integrity, that is, the greater the number of people the poorer the integrity.

The USGS is now planning a phase III study that will look at the effect of water quality on habitat integrity.

Mary Ellen Whitworth, former environmental aide to Houston mayor Bob Lanier, is executive director of the Bayou Preservation Association.