Keywords: Accretion, Compartmented breakwater. Continuous breakwater, 

 Currents, Hydraulic model (three-dimensional). Littoral 

 transport. Movable bed. Segmented breakwater, Tombolo, 

 Wave attenuation 



The two major purposes of an offshore breakwater are to prevent 

 erosion and to protect structures on the shore. Studies on offshore 

 breakwaters have included experiments in two dimensions, monitoring of 

 existing breakwaters, and determinations of transmitted wave heights on 

 submerged breakwaters. There are few studies on the three-dimensional 

 effects of offshore breakwaters on shore processes. 



This study determines the design and positioning of offshore break- 

 waters not only to prevent shore erosion, but to promote an accumulation 

 of littoral material to lessen the nearshore slope and to maximize the 

 area of the sandy beach. The model chosen for the study was Kasumi Bay, 

 northern Hyogo Prefecture, facing the Sea of Japan. Waves on this coa?t 

 occur mainly during the winter, caused by seasonal winds. When winter 

 storms pass through, the coast is subjected to continuous waves with 

 heights of several meters for periods of 2 to 3 days. 



132. NAGAI , S., and SEO, G., "Constructions of Small Commercial and 

 Fishery Harbours on Sandy Coasts in Japan," Report to SII-S2 

 (Means of Controlling Littoral Drift to Protect Beaches, Dunes, 

 Estuaries, and Harbor Entrances, Establishment of Artificial 

 Beaches), XXIIId International Navigation Congress^ Ottawa, 1973, 

 pp. 97-119. 



Keywords: Accretion, Hydraulic model (three-dimensional), Japan (Seppu) , 

 Littoral transport. Sand trap, Tombolo 



This report discusses Japanese fishery, one of Japan's primary 

 industries. Subjects of discussion include: Japan's geographical and 

 environmental conditions, the outline of the fishing industry and fishing 

 ports, a general idea of the fishing port construction on Japanese sandy 

 beaches, and two fishing ports as examples in recent constructions with 

 littoral drift problems and their countermeasures . 



133. NAKAMURA, M., SHIRAISHI, H., and SASAKI, Y., "Wave Damping Effect 

 of Submerged Dike," Proceedings of the 20th Conference on Coastal 

 Engineering, American Society of Civil Engineers, Vol. 1, 1966, 

 pp. 254-267 (also appeared in Proceedings of the 12th Conference 

 on Coastal Engineering in Japan, 1966, pp. 76-79). 



Keywords: Hydraulic model (two-dimensional). Submerged breakwater. 

 Wave attenuation, Wave transmission 



Wave energy is dissipated by a submerged breakwater when waves 

 break on the structure. Some of the remaining energy is dissipated by 

 reflection and friction on the crown of the submerged breakwater and 

 some is transmitted shoreward. In previously published reports, the 



46 



