For the purpose of determining the suitable arrangement of coastal structures planned for an expected recreational beach at Ito Coast, model experiments were conducted both on the variations of sea-bed topography and on the exchange of sea water inside offshore breakwaters.
　In the littoral drift experiments, a movable-bed model of 1/200 in horizontal scale and 1/100 vertical was formed with fine sand. An experimental wave which could reproduce long-term variations of the prototype sea-bed topography was initially determined through preliminary experiments. The variations of the bed topography caused by the waves were measured for the various arrangements of groins and offshore breakwaters placed on the nourished beach.
　In the sea-water-exchange experiments a fixed-bed model was formed in the same scales and the structures with the most suitable arrangement obtained in the littoral drift experiments were placed on it. Relatively small swells corresponding to the summer condition were applied in addition to the varying tidal current to make experimental conditions similar to prototype phenomena, and the diffusion of dye injected at the foreshore was investigated photographically.
　Finally a plan of the most suitable arrangement of the structures was proposed.