Tagonoura harbour is located in the most inner part of Suruga Bay and lies in the path of typhoons generated over the Pacific Ocean south of Japan. With its axis north and south and its mouth opening southward to the Pacific, the bay is extremely susceptible to flooding caused by large waves and typhoon surges.
　In the fall of 1966, Suruga Bay was attacked by the severe typhoon which generated very large waves, especially in front of Tagonoura harbour. Owing to the attack of large waves generated by this thyphoon, the front toe of the west breakwater was scoured out in 4.5m depth and the caisson of No.10 was inclined to the offshore direction.
　As the results of this disaster, the function of the west breakwater was missed in some degree, so that in order a to return the west breakwater to the normal condition and get the function of the breakwater as it was, a several methods for repair works were suggested from Shizuoka Prefecture, Port and Harobur Bureau and Port and Harbour Research Institute, Ministry of Transport, after detail discussions were made.
　In this report, the experimental results on the several repair work methods mentioned above have been discussed and some ideas to get the function of the breakwater which stands on a sandy sea bottom have been shown.
　The repair work methods used in the model experiment were as follows.
(1) to sink the caisson in front of the west breakwater in such a manner of getting the crown height of the caisson of -8.0m. The caisson is 14m in width, 17m in
height and 15m in length.
(2) to build new caisson type breakwater in the rear side of the west breakwater.
(3) to build Tetrapods mound with or without asphalt-mat under it in the front side of the west breakwater. The crown height of the mound is -7.0m and the width o
f crown is 10.5m.
　We got some usuful conclusions from this model experiment. In order to prevent the west breakwater from scouring, (1) method would be recommmended, but if it is considered only to get the whole function as the breakwater rather to prevent the west breakwater, (2) method would be recommended.