INVESTIGATIONS OF URBAN FLOODPLAIN SEDIMENT TEXTURE, DEPOSITIONAL RATE AND CONTAMINATION IN KNOXVILLE, TN

This abstract describes the preliminary results of an investigation of sedimentation, post-industrial disturbance, and contamination along two creeks in urban areas of Knoxville, Tennessee. Two public databases were used to identify land use and pinpoint areas of frequent flooding on public lands along First Creek and Third Creek in the Fort Loudoun Lake Watershed in Knoxville, TN. Both creeks drain urban and/or current and former industrial areas and discharge into an impounded section of the Tennessee River. Industrial and urban contaminants are often found in streams, but there is also potential for spreading of contaminants into floodplains during seasonal or extreme flood events via direct deposition of particles (for example coal tar) or deposition of clay particles with adsorbed contaminants. Samples were collected with a 5.1 cm diameter auger and 1.9 cm diameter core barrel at sites along the floodplains of First and Third Creeks. At the two sites along First Creek and the furthest upstream site along Third Creek, angular gravel particles with diameters of greater than 2.0 cm were present in large quantities. These appear to be fill materials, likely placed during construction of urban parks in the floodplain. Six other sites along the downstream reaches of Third Creek appeared relatively undisturbed, apart from minor surface grading during construction of urban parks and greenways. Sediments at these sites are dominated by silt and clay sized particles, which are typical of the weathered sedimentary rocks in this area. Sediment samples from the relatively undisturbed Third Creek sites will be sent to a lab for age dating using Cs-137 to determine approximate time of deposition and depositional rates. Grain size distribution and other characteristics, such as organic carbon content, will be measured. Thin sections will also be prepared and analyzed using techniques of soil micromorphology to look for anthropogenic indicators (like coal fragments) and to help distinguish flood deposits and buried soil horizons from fill or disturbed materials. A second round of sediment samples will be collected and analyzed for typical urban/industrial contaminants, such as coal tar compounds, petroleum hydrocarbons, lead, mercury and cadmium.