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Overtopping of Coastal Structures by Random Waves

Author(s): C. Memos; E. Pavlidis

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Keywords: Wave overtopping; Coastal defences; Random seas; Probabilistic approach

Abstract: Wave overtopping is a crucial factor in the design of coastal structures. Existing methods predict overtopping of random waves by use of empirical expressions that behave acceptably only within prescribed limits. Some of these approaches employ a wave-by-wave analysis of the random wave field and refer to the estimation of the respective values of overtopping by monochromatic waves, that in turn use results obtained for the wave run-up on slopes. In order to be able to “reconstruct” the wave field, the assumption is often made of a Rayleigh distribution of wave heights, which in shallow water is truncated according to the breaking wave height. This assumption, however, is not valid for non-narrow wave spectra, a common feature of real life wind-driven seas. Moreover, the wave periods are often assumed constant over all the monochromatic constituents of the wave field. In this study a refined probabilistic structure of the sea is used that allows the estimation of the joint density of wave heights and periods in sea states of any bandwidth in deep or shallow water. This is an advantage over existing approaches, as verified by comparisons with experimental measurements. It was found that in general the present model yields higher values of overtopping than existing methods, especially in wide-banded seas. In shallow water this deviation increases with increasing sea bed slope. Some trends of existing methods used in the calculation of wave overtopping or run-up were also identified.


Year: 2003

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