Beach profile changes in front of the gentle-slope sea dike and the damage of dike with them were studied experimentally by using the regular and irregular waves. Beach profile changes caused by irregular waves becomes smaller than that by regular waves. It will be considered that the beach profile changes are smoothed in general, because the wave breaking point for irregular waves is different every one wave. In the case of regular waves, although the damage of dike progresses gradually as a

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... me of wave action becomes longer, the damage becomes early with increasing dike slope. On the other, in the case of irregular waves, the damage of dike did not occur within the limits of this experiment.