Beach topography and nearshore current has been observed by video monitoring system since Aug. 2001 until Mar. 2007 in Sumiyoshi beach, Miyazaki, Japan. Recently, Sumiyoshi beach has been suffered from heavy beach erosion. In this study, long term change in bar topography in such an erosive beach is mainly analyzed. Also, the long term observation of longshore current is conducted in order to elucidate the longshore transport. The followings are the results obtained in this study.
1) There were two bars in Sumiyoshi beach since Aug.2001 to Jul.2003. The inner bar is located about 70m offshore and the outer bar is located about 300m offshore. Cyclic on-offshore movement of inner bar and rip channels was observed.
2) Alongshore patterns of bars’shape were observed. The patterns move alongshore 4m/day at the inner bar and 2m/day at the outer bar.
3) In Jul. 2003, the inner bar disappeared because of frequent attacks of typhoon and has not appeared since then until Mar. 2007.
4) The southward longshore currents frequently occur rather than the northward currents.