The problem of sand transport by a longshore current is clarified 

 by observing the effect of a breakwater on the current., Sand samples 

 were collected on a network from the beaches near the breakwater at 

 Santa Monica, California. The distribution of median grain sizes indi^ 

 cates a reduction of the competence of the longshore current, The his- 

 tory of shoreline changes discloses an accompanying reduction in the 

 capacity of the current. A decrease in transporting power of the long- 

 shore current is correlated with a decrease of Q, the littoral drift 

 factor; Q can probably be used as a qualitative measure of the sand- 

 transporting power of longshore currents. 



The history of accretion indicates that a shoreline changes position 

 in a direction toward equilibrium with respect to the forces acting on a 

 beach. Given enough time, it is probable that the breakwater will become 

 connected to the mainland. 



59. HARUTA, T., "Recent Coastal Processes in Niigata Prefecture," Coastal 

 E-ngineeving in Japan , Tokyo, Japan, Vol. IV, 1961, pp. 73-83. 



Keywords: Accretion, Detached breakwater, Downdrift beaches, Japan 



(Fuya, Hakahama, Ishiji, Iwafune, Kitaebisu, Nakahama, and 

 Neya) , Littoral transport, Structural dimensions, Tombolo 



The exposure of the coast of Niigata Prefecture to the winter mon- 

 soon of the Sea of Japan, which has the predominant direction from north- 

 west to north, is the most important factor affecting the beach erosion 

 or sand transport on this coast. Most of the coast has sandy beaches 

 nourished by sediment from rivers. There are some harbors and a number 

 of small fishery ports. The construction of breakwaters, groins, or 

 jetties in the harbors or ports caused certain changes in the patterns 

 of waves, currents, and littoral transport; thus, beach erosion or sand 

 deposition occurred in many parts of the coast. This paper presents 

 several examples of such coastal processes with a description of the 

 protection works applied. 



60. HASHIMOTO, H., "A Model to Predict the Influence of Erosion on 

 Neighboring Beaches Due to Detached Breakwaters," Tvooeedings of 

 the 21st Conference on Coastal Engineering in Japan, Japan Society 

 of Civil Engineers, 1974, pp. 181-186 (in Japanese). 



61. HASHIMOTO, H., "Application of a Beach Deformation Model to Fuji 

 Coast," "Proceedings of the 2Sd Conference on Coastal Engineering 

 in Japan, Japan Society of Civil Engineers, 1976, pp. 218-222 

 (in Japanese) . 



62. HASHIMOTO, H. , and UDA, T., "A Method of Numerical Prediction of 

 Nearshore Currents and its Applications," Troceedings of the 21st 

 Conference on Coastal Engineering in Japan, Japan Society of Civil 

 Engineers, 1974, pp. 355-360 (in Japanese). 



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