This paper introduces the general factors affecting the coastal 

 problems in Japan and discusses the patterns with which some of these 

 factors were linked to produce particular coastal problems. The efforts 

 and contributions made by the Japanese engineers to solve such problems 

 are discussed. The coastal protection works and practices are presented 

 with some representative examples. 



72. HOM-MA, M., and HORIKAWA, K. , "A Study on Submerged Breakwaters," 

 Coastal Engineeving in Japan^ Tokyo, Japan, Vol. IV, 1961, pp, 85- 

 102. 



KeifUords : Accretion, Compartmented breakwater. Concrete structures. 



Foundation design. Hydraulic model (two-dimensional), Japan 

 (Niigata) , Local scour. Movable bed. Structure settlement, 

 Submerged breakwater, Tetrapods, Wave overtopping. Wave 

 transmission 



The functions and maintenance devices of submerged breakwaters, 

 using tetrapods, were studied through the comparison of experimental 

 results and field data from the Niigata west coast. Since one of the 

 most important functions of a submerged breakwater is the damping action, 

 the structure has played an important role in protecting the Niigata west 

 coast. The slump of the structure, which was overlooked at the early 

 stage of construction, has become an important and difficult problem. 



73. HOM-MA, M., and SAKOU, T., "An Experimental Study on the Submerged 

 Breakwater," Coastal Engineering in Japan, Tokyo, Japan, Vol. 2, 

 1959, pp. 103-109. 



Keywords: Accretion, Hydraulic model (two-dimensional), Local scour, 

 Movable bed. Submerged breakwater, Vertical breakwater 



The two principle functions of a submerged breakwater are (a) to 

 attenuate waves by causing premature breaking and partial reflection, 

 and (b) to bar seaward movement of bed materials in the surf zone, Most 

 studies of these functions deal with the effects of the height, shape, 

 width, location, etc., of the breakwater on the transformation of passing 

 waves. However, the effect on the sand movement and deformation of the 

 beach due to the existence of the breakwater has not been sufficiently 

 studied. This study presents the basic information needed to predict the 

 possible change in beach profiles after the construction of a breakwater 

 and to estimate the amount of scour around the strqcture. This was 

 accomplished with a study of the two-dimensional deformation of a beach 

 in an experimental wave flume. 



74. HORIKAWA, K., and KOIZUMI, C, "An Experimental Study on the Func- 

 tion of an Offshore Breakwater," Proceedings of the 29th Annual 

 Convention, Japan Society of Civil Engineers, 1974, pp, 85-87, 



29 



