California Sea Grant College Program

In Southern California, terrestrial runoff pollution often drains directly onto the beach, degrading water quality and leading to increased beach closures each year. Beaches are a significant piston in California’s economic engine and beach closures can have significant economic impact on local communities. Runoff pollution can be localized, as from a storm drain, or can be more diffuse with many smaller, distributed sources. In either case, upon entering ocean waters, the pollution is first mixed, dispersed, and advected within the surfzone (the region of breaking waves). However, behavior of polluted waters upon entering the surfzone is not understood, and advancing this understanding is crucial to improved beach water quality.

The dispersion of passive tracers, such as pollutants, in the surfzone was be examined using both drifter observations and nearshore wave/circulation models with the goal of understanding the mechanisms of dispersion and to develop formulations for predicting dispersion.