SEDIMENT POLLUTION AND RESTORATION EFFECTIVENESS IN AN IMPAIRED URBAN CREEK

Water quality in urban creeks is often degraded by runoff and erosion, resulting in abnormally high levels of sediment pollution. The purpose of this study was to investigate whether bank restoration in impaired urban creek (Second Creek, Knoxville, Tennessee) was successful in reducing bank erosion and suspended sediment levels. We identified 3 sites representing pre and post restoration conditions, and we collected daily turbidity samples at each site from April 1 - September 1, 2021, (n=126). We also installed 8-inch galvanized stakes flush with the bank and measured the horizontal exposure in inches from April 1 to October 1, 2021 (n=6). Daily discharge was also measured. Turbidity data were transformed from NTU to total suspended solids (TSS) in mg/L and multiplied by discharge in L/s to attain mg/s of sediment. ANOVA tests compared the mean daily TSS readings and the erosion pins’ total horizontal change over time at each site (1-2, 2-3, 1-3). Results indicate that TSS did not show a significant change between sites (P=.90 1-2, P=.92 2-3, and P=.99 1-3), suggesting that erosion and deposition did not have a noticeable effect on daily readings between sites. When ranked by magnitude, 55% of daily turbidity readings were less than 10 NTU at all three sites. Discharge was positively related to TSS as follows: r-square value = .48 and statistical significance = 1.38E-19. There was a significantly larger horizontal change in the exposed erosion pins at unrestored site 1 when compared to site 3 downstream of the restored area (P= 5.63E-05), indicating that the restoration caused an effective decrease in erosion. This research gives initial insight into suspended sediment in a degraded urban creek and the effectiveness of restoration in reducing bank erosion. Our understanding could be improved by more sampling sites downstream and direct measurements of TSS. Furthermore, comparing Second Creek to other urban and pristine creeks in the area could give us a better understanding of the creek’s health and sedimentation levels, especially since state and federal standards for sediment levels are unclear.