Kazumasa Katoh, Shin-ichi Yanagishima


Breakers in the surf zone are saturated, that is, the wave height at any point is limited by the local water depth. The larger waves in a storm break further offshore making the surf zone wider but leaving the wave height in the inner surf zone the same. Why the beach will erode during the storm? To answer this question, there has recently been considerable interest in the long period waves of one to several minutes in period. The field observation has been carried out for more than one year to acquire the field evidences of berm erosion due to the long period waves. Based on the data obtained, two typical evidences of berm erosion will be shown. A critical level of berm erosion will be discussed, which can be predicted with the mean sea level and the height of long period waves at the shoreline.


long period waves; erosion; berm erosion

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