ANALYSIS OF MULTI-SCALE BEACH CHANGE

摘要

Multi scale beach change at Joetsu-Ogata Coast located in the Niigatha Prefecture, Japan, was investigated by using monthly cross shore beach profiles measured at this beach. Joetsu-Ogata Coast faces the Sea of Japan and is subjected to high energy wave conditions with strong winter/summer seasonal signature. The shoreline position seems to follow the seasonal variability of incident wave climate. During summer months, the beach profile variability occurs mostly in the sub-tidal part of the profile however, a significant amount of upper beach change can be seen during winter months. Average annual shoreline position show a long term beach accretion, however this trend doesn't show any correlation with incident wave climate and also available data are not enough to investigate this further. Empirical Orthogonal Function analysis of the profiles show that the variability of beach profile shape is dominated by (a) upper shore face steepening; (b) sub tidal berm development and dissipation; and (c) variability of the overall profile slope, which have some longer than seasonal cyclic signatures.