In constructing ports and harbors, the Eco-friendly function has been recently added on coastal structures in Japan. As leeward step with a sloping breakwater provides the suitable condition for seaweeds, it was reported to effective construction in formation of seaweed forest. However, leeward step must be stable against wave overtopping, it needs to be covered by armor units.
In this study, hydraulic model experiments clarified fluid motion occurred by plunging of wave overtopping, and the design method of armor unit was proposed.
