Year Established: 2019 Start Date: 2019-04-30 End Date: 2020-04-29
Total Federal Funds: $35,000 Total Non-Federal Funds: $70,000
Principal Investigators: Dr. Karen Prestegaard
Abstract: Stream confluences are sites where two tributaries meet or where a tributary joins a river main-stem. Stream morphology, sediment transport, and stream-floodplain interactions can change significantly downstream of confluences. Flow dynamics at confluences can regulate the transport of coarse and fine sediment from upstream tributaries. Bedload and suspended sediment are moved primarily during storm events, but dynamic interactions of stream hydrographs at tributary junctions can create backwater effects that influence energy gradients, shear stress, and sediment transport. Few studies of sediment transport through river confluences have been conducted in urban areas. Urbanization adds impervious surfaces and storm sewer networks to landscapes, increasing runoff volumes and decreasing the time to hydrograph peak discharges. Modifications of hydrograph lag times can modify arrival times of peak flows at tributary junctions, creating nearsimultaneous arrivals or reversing arrival time order. Tributary hydrograph dynamics can affect energy gradients and sediment transport through river confluences, which may modify the amount of coarse and fine sediment in downstream reaches. In this study, new data will be gathered to evaluate bedload movement through confluences. We will: a) use in-situ monitoring to evaluate storm hydrographs, energy gradients, and bed shear stresses required to transport from tributaries through stream confluences, b) track bedload with tracer particles including smart rocks with motion recorders, and c) use USGS hydrograph data to evaluate hydrograph changes due to urbanization in our study and adjacent watersheds. The research project will provide training for graduate and undergraduate students through class field exercises and as components of research projects.