that a countermeasure for beach erosion be considered for the beach opposite 

 the breakwater gaps, as this area is often eroded after breakwater installa- 

 tion. In later discussions of the Kaike coast project (Toyoshima 1976, 1982), 

 performance of the breakwaters is still considered successful, although 

 subsidence of the structures is reported to be a significant contributor in 

 reducing their efficiency. 

 Walker. Clark, and Pope (1980) 



25. Walker, Clark, and Pope discuss the method used to design the 

 Lakeview Park, Lorain, OH, segmented detached breakwater project for salient 

 formation. This technique, hereafter referred to as the Diffraction Energy 

 Method, involves construction of diffraction coefficient iCp isolines for 

 representative waves from predominant directions. Detached breakwaters along 

 the California coast, particularly the Venice breakwater, were observed to 

 have shorelines approximated by the intersection of K^ isolines equal to 

 0.3. Walker, Clark, and Pope theorize that storm waves, usually an order of a 

 magnitude greater than the average wave conditions, are able to transport 

 material at least as far shoreward as the average wave K^ equal to 0.3 

 isolines. Thus, these isolines are a good indicator of the likely shoreline 

 position. The Lakeview Park project was designed such that the iCp = 0.3 iso- 

 lines intersected lakeward of the project beach fill but shoreward of the 

 three breakwater segments, ensuring that tombolo formation would not occur. 

 Actual shoreline response to the structures was slightly different than had 

 been expected: the west end of the project beach was continually eroded, 

 despite beach-fill replenishment. The most likely reason for the discrepancy 

 between design and actual shoreline response, however, may not be the design 

 method itself but the wave climate chosen for design (USAED, Buffalo 1975; 

 Pope and Dean 1986) , as waves from the northwest were inappropriately 

 weighted. 



Pope and Dean (1986) 



26. Pope and Dean (1986) present bounds of observed beach response 

 based on prototype performance of seven US detached breakwater projects. The 

 occurrence of tombolo, salient, or nonsinuous beach response is given as a 

 function of two dimensionless parameters: the segment length-to-gap ratio and 

 an effective distance offshore- to -depth at structure ratio, where d is the 

 depth at the structure (Figure 4) . High- and low-water conditions are 



17 



