A22 



measured salients. The best agreement obtained is shown in Figure A 12, 

 which has a calculated CVE equal to 9.01. As shown in Figure A12, there is 

 an appreciable improvement in the agreement between the longshore locations 

 of the calculated and measured salients. However, the bayward limit of the 

 salients of the calculated shoreline needs to be increased, while the landward 

 limit of the embayments of the calculated shoreline needs to be decreased to 

 improve agreement with the measured shoreline. 



In an attempt to increase the bayward limit of the salients of the calculated 

 shoreline, the transmission coefficients of the breakwaters were decreased 

 from 0. 1 to 0.0, which represents no wave transmission through the 

 breakwaters. This change had a negligible effect on the location of the 

 salients. Next, the value of K 2 was increased from 0.25 to 0.50 and then to 

 0.75. The effect of these changes was an increase in the calculated CVE from 

 9.01 with K 2 = 0.25 to calculated CVE's of 9.20 and 9.88 with K2 = 0.50 

 and 0.75, respectively. This change also had a negligible effect on the 

 location of the salients. 



Following unsuccessful attempts at improving the agreement of the 

 bayward limit of the salients and the landward limit of the embayments, the 

 changes between the measured post-fill (July 8 1991) and the measured 

 September 28, 1991 shoreline positions were analyzed in more detail. As 

 shown in Figure A13, following the completion of the beach fill on July 8, 

 1991, the shoreline evolved to the position shown on September 28, 1991 as a 

 result of the influence of the breakwaters on the wave climate. As noted in 

 Figure A 13, an overall bayward movement of the shoreline occurred, 

 including the shoreline opposite the breakwater gaps. Although the bayward 

 movement of the shoreline leeward of the breakwaters was expected, the 

 bayward movement of the shoreline opposite the gaps was not anticipated. 

 Typically, the shoreline opposite breakwater gaps evolves landward to form 

 embayments in equilibrium with the diffracted wave climate with the sediment 

 eroded from the embayments forming the salients or tombolos behind the 

 breakwaters. 



In this case, the bayward movement of the shoreline opposite the gaps is 

 attributed to erosion of the storm berm constructed as a part of the beach fill. 

 The beach fill template consisted of a 20-ft-wide berm at +6.0 ft mlw with a 

 1V:8H slope from the bayward edge of the berm to the existing bottom. Site 

 visits following the beach fill placement and after some moderate storm events 

 revealed that 1- to 3-ft-high erosion scarps had occurred along the berm 

 opposite the breakwater gaps. The net effect was that the scarping and 

 erosion of the berm in these areas resulted in a movement of beach fill from 

 the berm to the offshore area to reduce the slope of the beach. As a result, 

 the mean low water (mlw) shoreline opposite the gaps advanced bayward in 

 all locations. 



In retrospect, a straightforward application of GENESIS would not be 

 expected to result in good agreement between the measured and calculated 

 shorelines because of the addition of sand to the mlw beach as a result of the 

 scarping. In an attempt to simulate this process, a simulation was made with 



Appendix A Case Design Example of Detached Breakwater 



