INFLUENCE OF LOW-FREQUENCY STANDING WAVES ON LONGSHORE BAR DEVELOPMENT

Field measurements of beach profiles and waves in the surf zone have been conducted for about two weeks to investigate the influence of the low-frequency waves on longshore bar migration. The beach profiles were measured daily every 5 m along a 400-meters-long pier, and the waves were measured almost continuously at five points along the pier. Spectral analysis applied to the wave data and a theoretical investigation showed that low-frequency standing waves or high-mode edge waves formed during storms. The frequencies of the peaks and valleys in spectral density, which correspond to those of the antinodes and nodes, respectively, were not influenced by the bar crest positions and did not change in spite of the seaward bar migration of about 70 m. The comparison between the positions of the bar crests and those of antinodes of low-frequency standing waves developed in the surf zone showed that the low-frequency standing waves had little influence on the seaward bar crest migration.