OBSERVATIONS ACROSS THE SAND-MUD INNER SHELF DURING THE MULTIPHASE TURBULENCE EXPERIMENT (MP-TEX 2019)

Reliable sediment transport models are vital for environmental management and restoration, natural hazard mitigation, navigation, and industry. Poorly incorporated, or absent, parameters in transport equations limit the accuracy and precision of predictions. Complex subaqueous environments have additional difficulties that limit data quantity and spatio-temporal resolution. We present the experimental design and preliminary results of a recent field campaign that explores cross-shore variation in velocity profiles and turbulence measurements throughout the benthic boundary layer to investigate sediment transport processes on a sand-mud shelf off of Ocean City, MD. Simultaneous observations were made of near bed hydrodynamic forcing from waves, tides, and currents with mixed sediments and bedforms. Preliminary analysis is focused on the methods of interpreting cross-shore variation in velocity profiles and turbulence estimates from five- and three-beam Acoustic Doppler Current Profilers (ADCPs) and Acoustic Doppler Velocimeters (ADV).

Instrumentation was deployed along a cross-shore transect for 45 days during the summer of 2019 that included four moorings locations to measure currents, waves, and turbulence (ADCP and ADVs), density, salinity, and temperature (CTDs and temperature sensors), bottom roughness (sonars), and concentration of suspended sediments (OBS) and sediments at the bed surface (conductivity array). Additional sediment stratigraphy data was obtained from sediment cores collected at three bi-weekly intervals. Velocity observations will be used to estimate the variation of turbulent kinetic energy (TKE), turbulent fluxes of momentum, and the bed shear stress throughout the observation period. The turbulence measurements will be related to the observed sediment concentrations and bed morphodynamic changes in future work. The combined hydrodynamic and sediment concentration observations will improve our understanding of sediment transport in a sand-mud sedimentary environment. The observations will also assist on-going efforts in developing high-fidelity physics-based numerical models for sediment transport of sand-mud mixtures.