Mitigation of Wave Overtopping Rate in Offshore Airport by Permeable Bed Type Seawall

Large wave overtopping due to storms sometimes causes heavy inundation damage in an offshore airport surrounded with the sea. The wave overtopping rate at seawall lines is significantly changed by the local sea bed topography and the type of seawall. In this paper the variation of wave overtopping rate along the seawall line including a corner part is studied in an experimental basin with a directional wave maker. In the later part of the paper, the countermeasures to reduce wave overtopping at the seawall are discussed. A seawall attached with a wave absorbing permeable bed behind it is proposed for the airport seawall and is investigated experimentally. Experimental results demonstrate the wave overtopping rate becomes remarkably small for the new type seawall.