In Motoineppu fishing port on the Okhotsk in Hokkaido, the outline facilities where the artificial formation of seaweed bed had been added were constructed, as a mitigation to which the natural seaweed bed disappears by enhancing the mooring basin. The doubly-placed breakwater, composed of a sloping breakwater and a gravity-type upright breakwater, was adopted in the outline facilities. By reusing the dredged rock, a mound for the artificial formation of seaweed bed was made behind the sloping breakwater. The crest depth of the mound is referenced to a depth of the natural seaweed bed around the port. This paper reports the effect of the artificial formation of seaweed bed and the effectiveness of the dredged rock on the monitor investigation from 2003 to 2011.
