NEAR-BOTTOM SEDIMENT RESPONSE TO COMBINED WAVE-CURRENT CONDITIONS, MOBILE BAY, GULF-OF-MEXICO

A two-hour length of near-bottom flow and sediment concentration data was collected in 6.05 m of water in the Gulf of Mexico neu Mobile Bay, Alabama, United States. The objective of this article is to present a comparison of the measured near-bed sediment concentration profiles with those predicted by the combined wave-current model of Glenn and Grant (1987). Acoustically sampled profiles of concentration were measured in the 90, 1.16-cm tall, bins composing the sampling volume. Measured currents were progressing toward the east and steadily increased to a value of 23 cm s-1 at the end of the deployment. Peak wave periods were 5.8 s, with significant wave heights of 80 cm and decreasing. The resulting profile comparisons, assessed by a reliability index, showed poor results in the first two 10-min frames and discouraging discrepancies for all frames above 10 cm above bottom. The near-bottom calculations steadily improved as time proceeded. A flux analysis revealed that the major discrepancies occurred when the model was making predictions for observed data which resulted from flow physics not included in the model. The sensitivity study revealed that the predictions were especially susceptible to small changes in the grain size distribution but not so for the resuspension coefficient gamma0, which has been frequently examined in other studies. (Acoustics, resuspension, fluxes, model.)