PRELIMINARY IDENTIFICATION OF ENVIRONMENTAL STRESSORS OF BRUSH CREEK, KANSAS CITY, MISSOURI

In response to its 1977, 1993 and 1998 tragic floods, tremendous engineering effort has been expended on Brush Creek, especially to its 6.5-mile-long downstream reach. In the past 10 years, 4 dams and 2 drop structures were constructed, resulting in an alternation of pools and dry-reach channels. These new pools provide opportunities for enhancing urban recreation resources but challenge the development of healthy aquatic ecosystems.

A preliminary list of candidate stressors includes: 1. stream geomorphology/configuration, 2. water temperature, 3. sedimentation, and 4. toxic concentrations of bioavailable metals. The paved channel bottom varies from 20 ft to 80 ft wide, with a central low flow channel. Tiers of concrete walls, with a bench from 4 to 10 ft wide protect some bank from erosion. Ten-foot-wide sidewalks extend along both banks. Most adjacent overbank is a narrow strip of grassed parkland with isolated mature trees, immediately bounded by spacious boulevards. This concrete configuration not only deprives most creek sections of the possibility of re-establishing riparian wetlands, but also exacerbates stressors 2 and 3. The lack of riparian shading, combined with warming effect from discrete dry reaches easily drives pool water temperatures to extremes during the summer. Temperatures exceeding 33 °C in dammed pools with air temperatures of 30 °C were recorded on some summer days (USGS-WRD). More summer water-temperature data need to be collected to characterize this stressor. Increased flow velocity due to the straightening of the creek causes an average of 15 cm/yr sedimentation in the pools. The sediment is mainly eroded from the remaining unpaved or sparsely vegetated banks. It is of concern that both bed sediment and bank soil contain high levels, respectively, of Cr (64.1-95.6 ppm, 47.1-98.4 ppm), Cd (70.7-626.8ppm, 109.4-565.7 ppm), and Pb (61.6-157.5ppm, 36.3-106.3ppm). However, the few available analyses of dissolved metal ions in the water column show relatively low concentrations (USGS-WRD). Further investigation is necessary to determine whether there is any significant seasonal concentration variation or release of these toxic ions from bed sediment. A cost-effective approach to mitigating the above stressors would be the development of a forested creek corridor.