Dispersion in the Surfzone: Tracer Dispersion Studies
2008
Feddersen, Falk
Terrestrial runoff and river input dominates urban pollutant loading rates. Often draining directly into the surfzone, this pollution degrades surfzone water quality, leading to beach closures (e.g., Boehm et al., 2002), increases health risks (e.g., diarrhea and upper respiratory illness) (Haile et al., 1999), and contains both human viruses (Jiang and Chu, 2004) and elevated levels of fecal indicator bacteria (Reeves et al., 2004). Surfzone mixing processes disperse and dilute such (and other types of) pollution. On smaller length-scales (smaller than the water depth), breaking-waves and bed-generated turbulence mix tracer. However, field surfzone observations of turbulence previously have been extremely scarce, and much about surfzone small-scale turbulence is not known. On larger scales (10-100 meters), horizontal dispersion is driven by surfzone eddies and meanders associated with shear waves (Oltman-Shay et al., 1989) or finite breaking crest length (Peregrine, 1998). Understanding the small and large length-scale mixing processes [is] important to predicting the fate (transport, dispersal, and dilution) of surfzone tracers whether pollution, bacteria, larvae, or nutrients.
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