Evaluation of Resuspension from Propeller Wash in Pearl Harbor and San Diego Bay

Abstract : Propeller wash induces disturbances to the bottom sediment in Department of Defense (DoD) harbors in multiple ways. Resuspension of bottom sediment, which is often contaminated, by propeller wash in DoD harbors is a phenomenon constantly observed and occasionally reported. While these resuspension events occur frequently, their effects on potential for erosion, transport, re-deposition, and re-contamination of bottom sediments have not been rigorously studied or quantified. This study aims to demonstrate and validate an innovative quantitative method that integrates information from state-of-science measuring devices/tools with predictive methods, including models. These measuring devices have been used to measure and evaluate critical parameters that govern propeller wash resuspension and subsequent fate and transport of the eroded sediments in DoD harbors. Accurate model results helped to reduce the uncertainty associated with propeller wash hydrodynamics and shear stress and resuspension potential of the sediment bed. Field data were used to support the fate and transport model, CH3D, which was successfully calibrated for San Diego Bay, CA; Pearl Harbor, HI; and Sinclair Inlet, WA. Once validated with the field data, CH3D was used to predict footprints (deposition) of the sediment plume and re-contamination potential from propeller wash. We have further extended the model's simulation and prediction capabilities on both the resuspension potential and fate and transport of the plume far and beyond the scenarios when the data were measured.