Cross-shore transport on gravel beaches

Kobayashi, NobuhisaPuleo, Jacks A.Coastal gravel can be found in both natural beach settings and in man-made protective structures like revetments. The experiment presented in this report was conducted in a wave flume to investigate the cross-shore evolution of gravel beaches under irregular laboratory wave conditions. A total of four tests were performed with varying initial beach profiles and incident significant wave heights. The first two tests were on an initially steep slope of 1/2 with two different significant wave heights, both of which created erosional conditions. The third test had an initially milder 1/5 slope resulting in beach accretion and the final test measured the onshore migration of a gravel bar. Each test consisted of either 18 or 36 wave bursts of 400 seconds, after which the profiles appeared to be quasi-equilibrium. Free surface and velocity data was collected and time-averaged for each 400 second wave burst and profile measurements were recorded for the initial, final and at least three intermediate profiles. The quasi-equilibrium profiles observed were similar in shape, but were affected by the differences in wave height and the initial profile conditions. Recorded hydrodynamic and profile evolution data was used for validation of a numerical model. The tests were designed to investigate the applicability of a numerical model developed for damage progression of stone armor layers to finer gravel material and to test the accuracy of the bed load formulation originally developed for a sand sediment transport model. The critical stability parameter used to determine movement for stone armors was found to predict profile change for the two erosion tests. The bed load formula required adjustment to better predict the amount and extent of onshore transport for the mild slope and bar migration test.University of Delaware, Department of Civil and Environmental EngineeringM.C.E