Abstract
Yatsushiro Bay is a typical closed bay on the west of the Kyushu Island, this sea area where a vast tidal flat develops. Recently, various environmental degradations are reported occur in Yatsushiro Bay, as red tidal and anoxic water. In this study, we tried the time series analysis of characteristic of the sediment, aim at the sea area environmental change characteristic in Yatsushiro Bay. As the result, the characteristic of the sediment in Yatsushiro Bay was classified into five patterns by the cluster analysis. The deterioration of the sediment being progressing in inner part of bay, near estuary and deep area in center part of bay became clear.
