Influences of an Enclosure of Bay on the Tidal Flat

As the finish of a sea dyke construction on April 14, 1997, the 35.5km^2 area of original Isahaya Bay has been divided from sea, and will be changed to field land in near future. The spatial distribution of tidal flat around the Isahaya Bay is considered to be affected severely. Thus, numerical simulations were carried out to examine and evaluate the influence of this action. Calculated results show that the shoreline in the Isahaya Bay varies as the decrease of water exchange between inside and outside of the sea dyke. Moreover, because of the slowdown of the current, sedimentation is occurred in front of the dyke, which implies the possibility of an appearance of tidal flat even since the area and thickness of the sediment controlled by the gate. It consequently indicates that adequate attention should be paid to preserve or produce the tidal flat