The experiments on a submerged breakwater are performed to investigate the characteristics of wave transformation behind the breakwater and the effects of the breakwater on wave overtopping. The main conclusions are given below:
1) The incident random waves break over the submerged breakwater and are transformed to small waves. The significant height of the transmitted waves keeps almost constant until their re-breaking take place in nearshore area.
2) The empirical formulas for the estimation of the transmitted wave height and the wave set-up are presented under the assumption of the linearity to hRT/H0', B
/Lo and Ho'/Lo.
3) The undulations like surfbeats is attenuated by the submerged breakwater, compared to the undulations without the breakwater.
4) The submerged breakwater is no more effective on the wave over-topping for the case of the water depth at vertical wall shallower than the transmitted wave height.
5) The estimation method for the wave over-topping rate is proposed by taking the wave transformation and the wave set-up behind the submerged breakwater into consideration.