Abstract
The coastal disaster due to wave overtopping was occurred in the Shimoniilawa coast faces to the Toyama bay in northern part of Japan in 2008. Several technical studies on the mechanism and the way of countermeasures have been justly reported. However, their consideration to wave transformations for over 14 seconds-period swell seem to be limited because they are based on a small model test using the simplified bathymetry or an ideal numerical simulation omitting hydrodynamics around submerged and detached breakwaters. In this paper, the large scale model test is carried out in the large basin set up the bathymetry model as fine as possible. The results indicate that the long period oscillations of water surface along the coast can make increase the wave overtopping and a coastal jetty can reduce the amplitude of them.
