Flushing Study of South Beach Marina, Oregon

A newly constructed single-opening marina was evaluated to determine flushing characteristics by comparison of a hydraulic model and a mathematical model with field studies of dye releases. Both models simulated well-mixed conditions and agreed well with each other. The dye study was conducted by mixing rhodamine-wt throughout the marina on a flood tide and monitoring dye concentration versus time over several tidal cycles following release. Over the initial 7-10 hours of the field studies, all three methods agreed well; field results thereafter showed three to six times less dye than model predictions. For marinas of simple geometry with single openings and width-to-length ratios similar to the marina studied here, flushing estimates may be conservatively approximated by elementary mathematical methods.