Mark W. Hancock, Nobuhisa Kobayashi


Experiments were conducted on a sand beach to represent occurrences of minor to major dune overtopping by varying the spectral peak period of incident irregular waves. Both water overtopping and sand overwash rates were measured. The experimental results were compared to existing empirical formulas for equilibrium beach slopes (Kriebel, Kraus, and Larson, 1991), cross-shore sediment transport (Kraus and Mason, 1993), and irregular wave reflection (Seelig, 1983) from sand beaches. Scale and non-equilibrium effects were found to be important causes of discrepancies between predicted and measured values. Additionally, an empirical formula for the overtopping of coastal structures (De Waal and Van der Meer, 1992) was compared with overtopping measurements for the experimental dune. The empirical formula of De Waal and Van der Meer gave order-of-magnitude estimates, but could not account for the effects of the profile evolution within each test. The measured average volumetric sediment concentration was found to be independent of the normalized overtopping rate and varied by only a factor of two.


overtopping; sediment transport; dune

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