It is common to cover a vertical part of a composite breakwater with wave-dissipating blocks when the breakwater is constructed in deepwater areas. However in these areas, the construction cost becomes quite expensive due to its volume of the structure. Therefore, we attempt to develop a new type of breakwater without wave-dissipating blocks in order to reduce the cost. In this paper, two-dimensional hydraulic model experiments are carried out to clarify the hydraulic characteristics of the reflected waves and transmitted waves, using the new type of breakwater. Two types of the structure are applied: “Sloping top caisson breakwater with sloped slit wall” and “Sloping top caisson breakwater with vertical slit wall”. The angle of the sloping caisson and slit wall is changed in several ways. The result of both experiments on reflected waves and transmitted waves is satisfied the chosen criteria.
