Abstract
The reclamation of land for making an island in a bay close to a big city sometimes causes the water pollution in the rear area between the island and the coastal line because of the water stagnancy. It is effective to generate one-directional current (a residual current) around the artificial island to promote the water exchange. The concept that the change of roughness according to the direction of tidal current produces the one directional avaraged current has been introduced. In this study, the most effective figure and arrangement of artificial roughness were made clear by carrying out experiments.
