Recently, the Bouyancy-driven vertical piling breakwater, which is proposed as a barrier for tsunami in original, is expected to apply as a drastic measure for harbor tranquility. In this case it is very important to consider its permeability for wind waves because it has a narrow gap between individual piles. In this paper, a sponge layer model and a porous layer model, those are often applied to partial wave reflection boundaries, are used as a permeable boundary in a Boussinesq wave model, and harbor tranquility is evaluated in an actual harbor. The porous layer model can reproduce both transmission and reflection rate with a standard gap but not with more wide or narrow gap. A numerically installed such breakwater can increase harbor tranquility in a whole year, but it is not enough in more severe seasons because its transmissivity is not so small.
