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EVALUATING AN URBAN STREAM RESTORATION PROGRAM FOR IMPROVING WATER QUALITY, IN-STREAM HABITAT, AND BANK STABILITY
Citation:
STRUCK, S. D., A. SELVAKUMAR, K. E. HYER, AND T. OCONNOR. EVALUATING AN URBAN STREAM RESTORATION PROGRAM FOR IMPROVING WATER QUALITY, IN-STREAM HABITAT, AND BANK STABILITY. Presented at 2006 American Water Resources Association, Mid-Atlantic Section Annual Conference, Branchville, NJ, June 14 - 16, 2006.
Impact/Purpose:
To inform the public
Description:
To improve water quality in urban and suburban areas, watershed managers often incorporate best management practices (BMPs) to reduce the quantity of runoff, as well as minimize pollutants and other stressors contained in stormwater runoff. It is well known that land use practices directly impact urban streams. Stream flows in urbanized watersheds increase in magnitude as a function of impervious area resulting in degradation of the natural stream channel morphology and affects the physical, chemical, and biological integrity of the stream. Stream bank erosion, which also increases with increased stream flows, can lead to bank instability, property loss, infrastructure damage, and increased sediment loading to the stream. This increased sediment load may lead to water quality degradation and have negative impacts on fish, benthic invertebrates, and other aquatic life in the stream. The EPA and USGS are investigating the effectiveness of stream restoration techniques including improvement of meander geometry and channel alignment, grade control structures, wing deflectors, increased channel habitat structure, and streambank stabilization (surface armor and vegetative methods, improved bank angle). These techniques are being considered as BMPs to improve bank stability and biological and in-stream water quality in the impaired urban watershed of Accotink Creek in Fairfax, Virginia. This multi-year project initiated in October, 2005 will continuously monitor turbidity, specific conductance, pH, and water temperature, as well as discrete samples of dry- and wet-weather flow chemical water quality parameters and biological samples in 5 sites (1 upstream, 3 within, and 1 downstream of the restoration reach) for 6 months pre- and 2 years post-restoration. In addition, physical parameters (e.g., pebble counts, longitudinal and cross sectional stream surveys) are being measured to compliment the chemical and biological constituents to assess the overall ability of the restoration to improve in-stream habitat. Pre-restoration results of wet-weather grab samples ranged between 1100 – 2800 cfu/100ml, 134 – 228 µS/cm, and 24.8 – 82.9 NTU for E.coli concentrations, conductivity, and turbidity, respectively. The dry-weather E.coli. sample concentrations, in comparison, were less than 1% of the average wet-weather sample. Similarly, the average turbidity value of 1.1 NTU for dry-weather samples was only 2% of the average turbidity of the wet-weather flow samples. The conductivity reading of 445 µS/cm was typical of dry-weather flow (and background) in the stream. Generally, there was an overall decrease in conductivity with wet-weather flow events. An exception to this occurred when a wet-weather event contained road deicing salts in which conductivity was more than 6500 µS/cm. Preliminary data indicate that a good predictive relationship can be made between turbidity and E.coli concentrations in Accotink Creek. The technique of using continuously collected data advances our understanding of the effects of stream restoration on water quality and quantity.