Breaking waves over barred profile with ripples

This paper presents an analysis of a series of laboratory measurements of horizontal velocity and suspended sediment concentration (arrayed vertically) at a number of locations across a simulated shallow water bar built in fine sands ([D.sub.50] = 95 [[micro]meter]) and subjected to irregular waves of varying significant wave height but with a constant spectral shape (JONSWAP spectrum). Near the bar crest the net suspended transport rates, integrated between the lowest measurement point and the water surface (measured zone), are dominated by the time-averaged (current-induced) transport resulting from undertow. Away from the bar crest the net suspended sediment transport in the measured zone resulting from high-frequency oscillatory currents is important (and dominant) and directed offshore everywhere. Comparison of the measured suspended transport rates and those derived from bed elevation changes over time reveals significant fluxes in the unmeasured zone near the bed. These are inferred as being driven by high-frequency oscillatory transport very close to the bed and are critical for understanding bar morphological changes. Finally, the laboratory results are compared with results from field experiments.