This report presents the experimental results on wave overtopping for Tagonoura sea-dyke.
　On the coast around Tagonoura port, sea-dykes are located 100～150m landward from shoreline with the crown height of 13.8～15m above LWL. At the time of typhoon No.26 in 1966, sea water invaded into the hinterland flowiong over not only the sea-dyke but also the sand dune about 100m behind the dyke. Thirteen lives were lost and the houses were severely damaged.
　A series of model experiments was carried out in order to study the phenomenon at the time of the disaster and to examine the following items proposed as preventive works against future disasters.
(1) Reinforcement and raising up the present sea-dyke
(2) Construction of the second wall behind the present sea-dyke
(3) Construction of the new dyke in front of the present one
　Model scale was 1:40 or 1:100, according to the object of the experiment and the characteristics of the available wave flumes.
　The special feature of Suruga Bay is the extremely big water depth near the shore and accordimgly steep beach slope of the order of 1:5. It is undoutful that huge waves directly attacked the beach and the dyke during the storm. The meteorological tide has little effect compared with the wave itself. Unfortunately, no definite wave record was obtained at Tagonoura port. The wave height for the experiment was determined so that the depth of flowing water over the sand dune in the model coincides the actural one, which was estimated to be nearly one metre from the field survey immediately after the disaster. As to the wave period, wave records at the adjacent port suggested the existence of relatively long peirod waves. Refferring to this fact, the experimental wave period was selected to be 20, 30, 40, 60,120 and 150 seconds. The wave height, determined by the above-mentioned method, ranges from 23m for 20 seconds to 4m for 150 seconds when converted into the equivalent deep water wave height.
　In the experiments, the volume of the water mass overtopping the dyke was measuered for each wave and for each crown heihght, profile and location of the proposed works. Thus, the effect of each proposal was quantitatively obtained as a guide to the future improvement of Tagonoura saa-dykes.