The Naha-harbor in Okinawa-Prefecture is located in a coastal region with coral reef where the wave transformation due to wave refraction, diffraction, shoaling and breaking are induced. The present harbor planning has been carried out employing only the wave diffraction calculation with a uniform water depth. Therefore the wave heights designed in some quay walls may differ from the practical wave situation. In the paper, a new wave simulation in the harbor area is carried out employing the new Boussinesq form named NOWT-PARI to evaluate the effect of an offshore permeable type breakwater with good accuracy. The simulated results are validated by the field observation carried out after the implementation of the breakwater in 2007.
