Experiment on Reduction of wave Overtopping Rate by Seawall with Double Parapet and Permeable Layer

Abstract

Several offshore airports in the Japanese coasts are often damaged+these days by the wave overtopping due to storm s. One of the problems in such offshore airports is the limitation of seawall crown height derived from the width, height and distance of runway. Minami et al.(2007) have proposed a new typ. seawall with a wide permeable layer behind the front parapet to reduce the wave overtopping rate. In this paper, an experiment in a directional wave basin is carried out to determine the most appropriate width of permeable layer and height of its backward parapet. The experimental results reveal that the wave overtopping rate becomes smaller than the allowable level as the permeable layer becomes wider than 6m. The backward parapet has to be higher than 2.5m to prevent the overflow into runways.