Date of Award
Master of Science
John S. Schwartz, Jon M. Hathaway
Christopher G. Wilson
Sediment is the most prevalent pollutant in waterways in the United States. Construction sites and roadways have both been identified as considerable contributors to sediment pollution, as they experience 10 to 20 times more soil loss than agricultural sites; however, this erosion can be mitigated through the utilization of best management practices, including erosion prevention and sediment control devices. An estimation of soil erosion can be determined empirically through the revised universal soil loss equation (RUSLE), the industry standard, or via a deterministic model, the water erosion prevention project (WEPP), to determine the optimal sediment control device to employ. Due to RUSLE’s empirical nature, limitations are created because of its reliance on field observations and physical experimentation to determine the correction factors; however, WEPP can simulate models representing these physical experiments to determine these same factors. In this study, WEPP was used to determine the highly debated erosion control practices factor (P-factor) for RUSLE. A variety of different parameters influence the efficiency of these sediment control devices, including drainage area, climate, soil types, topography, and land use/cover. This study focused on a combination of five common soil types (clay loam, silt clay loam, silt clay, silt loam, and loam) and four climate regions (Knoxville, Nashville, Chattanooga, and Memphis) in Tennessee to generate P-factors for silt fences and straw-filled sediment tubes. The study was performed by generating and calibrating a hillslope model, performing numerical simulations for a generated watershed, and determining and analyzing the P-factor. While no significant fluctuations of the P-factor for the different climate regions were found, there were significant differences for the soil type. The soil type was concluded to have the greatest influence on the efficiency of these sediment control devices due to variations in soil composition and hydraulic conductivity. The soil type with the greatest efficiency was silt clay loam (P= 0.34 for silt fences), while silt loam produced the least level of reduction (P=0.55 for straw-filled sediment tubes). Both tables and regression equations were created to model the P-factor for each combination of climate and soil type.
Abercrombie, Karen W., "Quantifying Support Practice Factor Values for Sediment Retention Devices Using WEPP. " Master's Thesis, University of Tennessee, 2022.