The seawall has been constructed at Karasu district of Tsu-Matsusaka port on the west side of Ise bay, because of the present seawall is getting decrepit. In front of the seawall is sandy beach, however, the sand fill will be done as an Integrated Shore Protection System at the part where less beach width, and also the Gravity Drainage System for beach stabilization will be constructed to keep the fill sand. Gravity Drainage System is the beach protection technique of controlling a groundwater level by burying a permeable layer under the foreshore. The design method of Gravity Drainage System is not established because there are less construct precedents of this system at the field. Accordingly, they buried permeable layer partially at the field and carried out the field observation for designing the Gravity Drainage System. But they could not take enough data to investigate the plane arrangement because of the field observation carried out narrow area. This three dimensional hydraulic model experiment were done to investigate the necessity of beach protection works and the adequate plane arrangement.
