California beaches which are extensively used for recreation and tourism and provide a significant contribution to California's economy, are sometimes impacted by poor water quality. In many urban locations, polluted runoff drains directly onto the beach, and is then advected and mixed into ambient waters by waves, currents, and tides. In cases with a known pollutant source, the direction of pollutant transport in the surfzone can be predicted based on environmental factors such as wave height and direction, and wind speed and direction; however, the details of pollution transport and dispersal are not understood and specific downstream locations affected by pollution cannot be predicted. As part of the HB06 project, a Southern California Coastal Ocean Observing System (SCCOSS) nearshore field experiment, surfzone wave and current observations were collected, confirming the accuracy of a model that provides real-time estimates of breaking wave heights and mean alongshore currents in the surfzone. Although this model can be used to predict average alongshore transport of pollutants, little is known about tracer dispersion and dilution in the surfzone region.
Oceanographers from Scripps Institute of Oceanography will use a unique GPS- and fluorometer-equipped jetski, frame-mounted fluorometers, and bottle samples to improve the understanding and modeling of tracer dispersion in the nearshore and surfzone, where breaking waves can drive intense mixing and strong mean circulation. The principle investigators will use dye concentration maps and multi-particle drifter data to estimate dispersion statistics, and to explore their dependence on wave conditions and other environmental factors. They will also utilize numerical models to explore dispersion mechanisms, such as breaking waves, rip currents, and shear waves. The results are expected to provide a better understanding of surfzone dispersion statistics and improved physics-based numerical models.
The surfzone modeling and analysis techniques resulting from this project could become an important management tool used in making decisions regarding beach closures. Several educational opportunities will also result from this research. The principle investigators will disseminate their findings to K-12 students and teachers through several programs including the Ocean Institute's Surfscience Teen Conferences.
