Longshore sediment transport rate calculated incorporating wave orbital velocity fluctuations

Laboratory experiments were performed to study and improve longshore sediment\ntransport rate predictions. Measured total longshore transport in the laboratory was\napproximately three times greater for plunging breakers than spilling breakers. Three\ndistinct zones of longshore transport were observed across the surf zone: the incipient\nbreaker zone, inner surf zone, and swash zone. Transport at incipient breaking was\ninfluenced by breaker type; inner surf zone transport was dominated by wave height,\nindependent of wave period; and swash zone transport was dependent on wave period.\nSelected predictive formulas to compute total load and distributed load transport\nwere compared to laboratory and field data. Equations by Kamphuis (1991) and Madsen\net al. (2003) gave consistent total sediment transport estimates for both laboratory and\nfield data. Additionally, the CERC formula predicted measurements well if calibrated\nand applied to similar breaker types. Each of the distributed load models had\nshortcomings. The energetics model of Bodge and Dean (1987) was sensitive to\nfluctuations in energy dissipation and often predicted transport peaks that were not\npresent in the data. The Watanabe (1992) equation, based on time-averaged bottom stress, predicted no transport at most laboratory locations. The Van Rijn (1993) model\nwas comprehensive and required hydrodynamic, bedform, and sediment data. The\nmodel estimated the laboratory cross-shore distribution well, but greatly overestimated\nfield transport.\nSeven models were developed in this study based on the principle that transported\nsediment is mobilized by the total shear stress acting on the bottom and transported by\nthe current at that location. Shear stress, including the turbulent component, was\ncalculated from the wave orbital velocity. Models 1 through 3 gave good estimates of\nthe transport distribution, but underpredicted the transport peak near the plunging wave\nbreakpoint. A suspension term was included in Models 4 through 7, which improved\nestimates near breaking for plunging breakers. Models 4, 5 and 7 also compared well to\nthe field measurements.\nIt was concluded that breaker type is an important variable in determining the\namount of transport that occurs at a location. Lastly, inclusion of the turbulent\ncomponent of the orbital velocity is vital in predictive sediment transport equations.