The experiment study on the influence of the offshore submerged breakwater to the wave run up on triangular step dyke was complete in this study. The crest width of the trapezoidal submerged breakwater b = 10,20,30 cm. The submerged depth of the submerged breakwater D = 10, 20, 30 cm and the distance from the center of the submerged breakwater to the toe of the dike L = 200, 300,400 cm was choiced to test respectively. The incident wave was irregular wave of P-M spectrum in #different range of wave steepness. Result shows the influence of the submerged depth of the submerged breakwater to the wave run up on smooth or step dyke was the biggest factor. The influence of the crest width of trapezoidal submerged breakwater as well as the installed distance of the submerged breakwater to the toe of the dyke for the relative run up height on the dyke surface was small.
Submerged breakwaters are simply the structures constructed with a crest elevation below the local water level. The purpose of the submerged breakwater was to reducing the incident wave conditions after the wave: transport over the breakwater. Due to the incident wave energy was relduced, so that the wave runup height on the sloping dyke will be decreased down also. At the second, the roughness of the sloping dyke can decrease down the wave runup height was studied by many researchers at the past time. One of that was the step dyke. Based on the result of the study confirm that it can reduce the wave runup height very much. In this study, the model test of the wave runup height on the step dyke surface in the wave condition that the incident wave was pass over the submerged breakwater was carry out.
