Wave Breaking and Dissipation in the Nearshore

The long-range goal of this research is a predictive understanding of the spatial and temporal variability of wave breaking in the nearshore, and the impact of wave breaking on the forcing of mean and oscillatory flows, sediment transport, and changes in large-scale nearshore morphology. The specific scientific objectives of this project are as follows: (1) improved modeling of wave transformation, wave breaking distributions, and surface wave stress on barred bathymetry; (2) improved understanding of infragravity waves, their forcing by modulations in wave breaking patterns, and their cross-shore variation across the surf zone; and (3) pilot measurements of wave breaking on the inner shelf. The difficult problem of understanding wave dissipation in the nearshore is approached through field observations made across a variety of beach profiles and under a wide range of wave conditions. Data are obtained remotely from video recordings of the surf zone and inner continental shelf, and image processing techniques are used to detect and quantify wave breaking over spatial and temporal scales ranging from 10-1000 meters and from 10-10000 seconds. The observed spatial distributions of ensemble-averaged wave breaking distributions are used to improve numerical dissipation estimates, and are subsequently applied to parametric models of incident wave energy transformation and mean current forcing within the surf zone. The forcing of low-frequency oscillatory motion through spatial and temporal variations of the point at which a wave breaks is being approached through a combination of theory and observation. The relationship of wave breaking to sediment transport is being pursued through co-located video observations and collaborative in situ measurements of sediment concentration, turbulence, and void fraction (air concentration).

See also ADM002252. The original document contains color images.