u 



Keywords: Accretion, Armor units, Compartmented breakwater, Downdrift 



beaches. Littoral transport. Local scour. Rubble mound. Struc- 

 ture settlement. Submerged breakwater. Wave attenuation. Wave 

 transmission 



Beach erosion is a serious problem on the Niigata Coast where the 

 shoreline has receded more than 300 meters during the past 50 years. 

 This tendency was accelerated after the completion of a floodway on the 

 Shinano River which caused a considerable decrease of sediment supply 

 to this coast . A submerged breakwater was constructed about 500 meters 

 from the shoreline to protect the eroded coast. This paper discusses 

 the effect of the breakwater on wave transmission and on the deposition 

 of sand, using the results of field observations by the Office of Shinano 

 River Works, Niigata Prefecture. 



159. SHIRDAN, L., Untitled report to SII-Sl (Breakwaters With Vertical 

 and Sloping Faces. Measurement of Waves. Study of Wave Forces. 

 Methods of Calculation) , XXIst Intevnationat Navigation Congress^ 

 Stockholm, 1965, pp. 101-109. 



Keywords: Accretion, Armor stability, Composite structures. Construction 

 procedures. Detached breakwater. Gabions, Israel (Nahariya and 

 Tel Baruch-Tel-Aviv) , Local scour, Rubble mound, Structural 

 dimensions. Wave attenuation. Wave overtopping 



Failures of low breakwaters are often induced by washouts of the 

 landward slopes by overtopping waves. A low breakwater at Nahariya, 

 Israel, was damaged on numerous occasions and a successful treatment 

 for the landward slope was not found until PVC-coated gabions were tried. 

 The results have been promising. The use of gabions on the landward slope 

 has been introduced into the design of a .similar structure at Tel Baruch. 



160. SILVESTER, R. , "Offshore Breakwaters," Journal of the Waterways and 

 Harbors Division^ Vol. 83, No. WW3, Sept. 1957, pp. 1368-1--1368-15. 



Keywords: Accretion, Detached breakwater. Hydraulic model (three- 

 dimensional). Littoral transport, Tombolo, Wave attenuation. 

 Wave diffraction 



The determination of wave heights and patterns for waves diffracted 

 by an infinitely long breakwater, or by a breakwater gap, has been based 

 on the theoretical solution for optical diffraction. Correct results 

 are obtainable at distances in the shadow zone many wavelengths from the 

 breakwater, but within an area of three wavelengths the results are 

 erroneous. Offshore breakwaters of limited length njust be studied if 

 their use in preventing beach erosion is to be successful, The main 

 factor to be considered is the wave pattern close to the breakwater. 

 Model tests for wave patterns with two different lengths of breakwater 

 and waves of different steepnesses are described and results presented 

 in a form suitable for application. 



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