Coupling alongshore variations in wave energy to beach morphologic change using the SWAN wave model at Ocean Beach, San Francisco, CA

Abstract

Coastal managers have faced increasing pressure to manage their resources wisely over the last century as a result of heightened development and changing environmental forcing. It is crucial to understand seasonal changes in beach volume and shape in order to identify areas vulnerable to accelerated erosion. Shepard (1950) was among the first to quantify seasonal beach cycles. Sonu and Van Beek (1971) and Wright et al. (1985) described commonly occurring beach states. Most studies utilize widely spaced 2-D cross shore profiles or shorelines extracted from aerial photographs (e.g. Winant et al., 1975; Aubrey, 1979; Aubrey and Ross, 1985; Larson and Kraus, 1994; Jimenez et al., 1997; Lacey and Peck, 1998; Guillen et al., 1999; Norcross et al., 2002) to analyze systematic changes in beach evolution. But with the exception of established field stations, such as at Duck, NC (Birkemeier and Mason, 1984), and Hazaki Oceanographical Research Station (HORS) in Japan (Katoh, 1997), there are very few beach change data sets with high temporal and spatial resolutions (e.g. Dail et al., 2000; Ruggiero et al., 2005; Yates et al., in press). Comprehensive sets of nearshore morphological data and local in situ measurements outside of these field stations are rare and virtually non-existent on high-energy coasts. Studies that have attempted to relate wave statistics to beach morphology change require some knowledge of the nearshore wave climate, and have had limited success using offshore measurements (Sonu and Van Beek, 1971; Dail et al., 2000).