Seiii. Uda. and Tanaka (1987) 



30. Based on a survey of over 1,500 breakwaters in Japan, Seiji, Uda, 

 and Tanaka (1987) predict the following gap erosion relationships, where gap 

 erosion is defined as retreat of shoreline to the lee of the gap from the 

 initial (preproject) shoreline position: 



— ^ < 0.8 no erosion opposite gap (30) 



0.8 ^ — ^ i 1.3 possible erosion opposite gap (31) 



— 2 ^1.3 certain erosion opposite gap (32) 



Noble (1978) 



31. Noble (1978) evaluated the effects of detached structures along the 

 California coast and those discussed in the literature and concluded that 

 "detached breakwaters produce only minimal impact when the offshore distance 

 of the structure is greater than six times the breakwater length." That is, 



— ^ s — minimal impact (33) 



X 6 



Noda (1984) 



32. Noda (1984) conducted a series of movable-bed (0.2-mm sand) 

 laboratory experiments evaluating physical parameters controlling the develop- 

 ment of tombolos and salients, especially due to on-offshore transport. Noda 

 used both storm and swell-type waves and concluded that maximum deposition 

 occurs when 



0.5 s — s 1.0 (34) 



21 



