Mean Currents and Sediment Transport at DELILAH

by Katherine A. Scott, Univ of California, Santa Cruz, United States,
Edward B. Thornton, Univ of California, Santa Cruz, United States,
William Birkemeier, Univ of California, Santa Cruz, United States,

Document Type: Proceeding Paper

Part of: Coastal Sediments


Bailard's sediment transport model (1981) is used as a framework to test the hypothesis that mean currents can dominate nearshore sediment transport. The data acquired during the DELILAH field experiment is used to calculate the contributions from long-wave (low frequency), short-wave (incident wave) and mean currents to the various moments following work by Guza and Thornton (1985) and Roelvink and Stive (1989). The DELILAH bathymetry was observed to contain a distinct accretional event followed by a prominent erosional event. As a preliminary analysis, two-hour velocity records were chosen to represent the morphological events, and were analysed for the correlation between the bathymetric changes and the velocity field. The incident wave component dominated the low-frequency component across the instrumented cross-shore profile during the two time periods, except at the innermost sensor during the time period chosen to represent the erosional event. The mean cross-shore and longshore velocities were larger by almost a factor of 5 during the more energetic record in the erosive event as compared with the record during the accretion event, lending evidence to support their role in the observed deflation of the beach face and the formation of the linear bar structure.

Subject Headings: Sediment transport | Erosion | Beach accretion | Long waves | Bathymetry | Shores | Water waves | Littoral drift

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