This study aims to investigate the characteristics of wave force on the seawall with a large-scale artificial reef, in Shimane Nuclear Power Plant facing to the Sea of Japan. Field observations were carried out to measure the wave field and the wave pressure on the seawall. The fission of the primary waves with the wave propagating on the reef causes the increase of the amplitude of the long period waves. It turns out that the wave force on the seawall increases in proportion to the amplitude of the long period waves. Moreover, the availability of the numerical analysis of CADMAS-SURF/3D was showed from the conformity with the observation result.
