Ocean-Outfall Mixing Zone Delineation Using Doppler Radar

Abstract

A methodology has been developed to use data collected by ocean surface current radar (OSCR) systems to predict the fate and transport of pollutants released from ocean outfalls. The proposed OSCR-based transport model was validated at the Miami Central-District (MCD) outfall using data collected during the Southeast Florida Outfall Experiment II (SEFLOE II). A comparison between the measured dye concentration versus distance from the outfall and the predictions of the OSCR-based transport model showed good agreement. A second validation test of the OSCR-based transport model compared the growth of variance versus time and diffusion coefficient versus length scale with the conventional Okubo diagrams for instantaneous tracer releases. This comparison indicated that the mixing characteristics simulated explicitly by the OSCR-based transport model are in good agreement with field measurements in the coastal ocean. Mixing zones based on worst-case and probabilistic criteria were delineated using the OSCR-based model. The results indicate that an OSCR-based transport model is a significant improvement over conventional models that are used to delineate mixing zones surrounding ocean outfalls with surfacing plumes. This claim is strongly supported by the field data collected during the SEFLOE II study in south Florida.