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Longshore Sediment Transport Rate Calculated Incorporating Wave Orbital Velocity Fluctuations
ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS COASTAL AND HYDRAULICS LAB
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Laboratory experiments were performed to study and improve longshore sediment transport rate predictions. Measured total longshore transport in the laboratory was approximately three times greater for plunging breakers than spilling breakers. Three distinct zones of longshore transport were observed across the surf zone incipient breaker zone, inner surf zone, and swash zone. Transport at incipient breaking was influenced by breaker type inner surf zone transport was dominated by wave height, independent of wave period and swash zone transport was dependent on wave period. Selected predictive formulas to compute total load and distributed load transport were compared to laboratory and field data. Equations by Kamphuis 1991 and Madsen et al. 2003 gave consistent total sediment transport estimates for both laboratory and field data. Additionally, the CERC formula predicted measurements well if calibrated and applied to similar breaker types. Each of the distributed load models had shortcomings. The energetics model of Bodge and Dean 1987 was sensitive to fluctuations in energy dissipation and often predicted transport peaks that were not present 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 was comprehensive and required hydrodynamic, bedform, and sediment data. The model estimated the laboratory cross-shore distribution well, but greatly overestimated field transport.
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