Sediment fate and transport models are often utilized to help address environmental questions related to the environmental impacts of remediation efforts, the potential for reliable natural recovery, and the potential impacts of extreme events. In order to effectively implement sediment fate and transport models, bed erosion and deposition rates must be accurately parameterized. These processes are dependent on physical forcing, the distribution of sediment in the water column, and the properties of sediment such as bulk density, particle size, and biogeochemical composition. This research will employ high-resolution numerical simulations along with analysis of in-situ measurements of physical processes and particle characteristics to quantify turbulent forcing and particle properties affecting sediment resuspension, settling, and flocculation. The project links academic-level researchers directly with practitioners actively involved with several USEPA Superfund sites and indirectly with environmental researchers, engineers, and policy makers. The project will support the Ph.D. research of two graduate students who will be advised by a diverse group and trained in advanced computational fluid dynamics, acoustic and optical field instrumentation, as well as practical aspects of environmental engineering. Results from this study will link methods and results from academic research to practice, enabling application of novel methods for quantifying and predicting sediment and contaminant fate and transport to present-day contaminated sediment sites. Additionally, the PIs have worked extensively with community modeling efforts and have contributed sediment transport modules to the Environmental Fluid Dynamics Code (EFDC), a state-of-the-art hydrodynamic model in use by the USEPA.
In this project, novel in-situ acoustical and optical instrument platforms will be deployed and laboratory experiments will be conducted to measure the physio-biogeochemical characteristics of flow and sediment in a turbulent, current and wave-driven shallow estuarine setting. Acoustic instrumentation will measure vertical distributions of mean flows and turbulence throughout the water column, including within the boundary layer, due to currents and waves. These will be combined with a floc camera and optical instruments that measure settling flux, particle size distributions and particulate biogeochemical compositions. Laboratory experiments will measure erosion rates and bulk densities of in-situ sediment cores. The field and laboratory observations of the sediment characteristics will be used to inform a high resolution large-eddy simulation (LES) model that resolves the details of the turbulent, sediment-laden boundary layer. The suite of data obtained from the field observations, laboratory experiments, and LES model will be used to understand the relationship between particle size distributions and turbulence in wave-driven estuarine environments and how these dynamics are affected by biogeochemical properties of the suspended particles. These dynamics will in turn be related to properties of the bed to understand how the turbulence and particle size distributions affect erosion rates. Finally, the LES model will be used to understand flocculation dynamics and the effects of sediment-induced stratification that may act to dampen the near-bed turbulence and reduce subsequent erosion and entrainment of sediment into the water column.
