Water Resources Research Act Program

Details for Project ID 2017TN130B

Sediment Source Tracking in Urban Watersheds: An Applicationin the Second Creek Observatory

Institute: Tennessee
Year Established: 2017 Start Date: 2017-03-01 End Date: 2019-02-28
Total Federal Funds: $8,964 Total Non-Federal Funds: $17,806

Principal Investigators: Jon Hathaway, Thanos Papanicolaou, Christopher Wilson

Project Summary: As urbanization spreads throughout Tennessee, the effect of land use change becomes evident in the form of increased stormwater runoff, pollutant export, and stream degradation. Numerous studies have been performed to better understand these effects and develop methods for their amelioration, but gaps in knowledge still exist. Although the field of urban hydrology is relatively mature, the same cannot be said of urban water quality modeling. Recent studies have shown that current models of sediment export from urban watersheds do not perform well,necessitating new approaches to improve these models. These efforts are hampered by the high spatial variability of land uses in these watersheds, as well as the presence of stormwater conveyance infrastructure which greatly influences system connectivity and conveyance. All these variables lead to difficulty determining sediment source areas for individual storm events. However, sediment source tracking holds promise to aid in understanding these processes. This method has become a recognized tool for determining sediment source areas, but has been performed rarely in urban applications. This study will rely on the Second Creek Observatory to help facilitate an effort to better understand the source of sediments in urban stormwater. Source material from around the watershed will be collected, including samples from construction sites, residential property, and roadways. These samples will be analyzed to determine their isotopic fingerprint. At the same time, three storm events will be monitored at the outlet of the watershed. These events will be well characterized by collecting around 20 samples per event. These samples will also be analyzed to determine their isotopic fingerprint. A mixing algorithm will be applied to these data to determine the sources of sediment for each sample collected during each storm. This will allow an understanding of where the sediments from each portion of the storms originate. These events will also be modeled with methods being developed at the University of Tennessee to better understand and predict small scale hydrologic processes. Through these methods, for each event, the source of runoff will be estimated. The estimated sediment source areas via the isotope analysis will be compared to the hydrologic methods to determine their agreement. If good agreement is discovered, these methods may provide insight into how sediment may be better modeled in urban watersheds by more accurately estimating runoff (and thus sediment) source areas. The objective of this research is twofold; (1) to better understand the sources of sediment in an urban watershed in Tennessee to inform management strategies and develop a methodology for similar studies elsewhere, and (2) to use this initial study as a way to develop new hypotheses for improving water quality modeling in urban watersheds.