RESEARCH ON THE ENIVIRONMENTALLY-FRIENDLY BREAKWATER USING A SUBMERGED BANK IN HAKODATE FISHING PORT - A FACTOR FOR THE FORMATION OF SEAWEED BED AND AN EFFORT OF THE SUBMERGED BANK -

Abstract

 The north breakwater of Hakodate fishing port located in the southwest region of Hokkaido was built in the 60's and becoming superannuated. There is a problem with the safety mooring of fishing boats and pleasure boat by the overtopping waves. So in order to solve this problem, the improvement work of the north breakwater has implemented as of 2010. In terms of the improvement, we adopt the doubly-placed breakwater that put the submerged bank in front of gravity-type composite breakwater and add a feature of artificial formation of seaweed bed because of isoyake is occurring with frequency around the north breakwater. And we set the crest elevation of the submerged bank to D. L. -0.1m in consideration of the flow velocity that could control feeding behavior of sea urchin. In this research, we report a controlled effect of the wave's flow velocity around submerged bank by the wave and current observation after building of the submerged bank has been completed.