Mechanisms and Countermeasures for Local Amplification of Long Period Waves due to Alongshore Change in Nearshore Bathymetry

Laboratory experiments were conducted for the concentration of long period waves due to sudden alongshore change in nearshore bathymetry. Waves and currents were measured around a boundary between mild and steep sloping beds. Alongshore variation in wave run-up showed significant peaks near the boundary, which were developed by the interaction of waves with nearshore currents and the excitation of long wave components by breaking group waves. Introduction of shore protection structures on the mild slope side was found to be effective in decreasing run-up heights on the steep slope side.