364. Line D . 1 . Because the two groins are relatively short, they are 

 specified to be nondiffracting. (In the process of model calibration, the 

 groins can be easily changed to be diffracting to check model sensitivity to 

 this assumption.) 



365. Lines D.4 and D.5 . The configurations of the groins are read from 

 aerial photos and checked with construction plans. 



366. Line F . 2 . Profile surveys made from October 1977 through November 

 1979 showed that the bottom slope was about 1:20 behind the detached break- 

 waters and 1:15 in the region of the gaps between the breakwaters. The chosen 

 slope, taken as an average for the whole area, is 1:18. 



367. Line F.3 . The east groin was built to be tight to prevent sand 

 from leaving the beach. It is assumed that permeability of the groins is low 

 and little sand transmission by overtopping occurs. 



368. Lines F.4 and F.5 . The amount of sand entering the project area 

 from the lateral boundaries is primarily controlled by the values assigned to 

 the lengths of the groins as measured from the shoreline position on the outer 

 side of the grid. Initial values of these lengths are taken from the aerial 

 photographs, but might change slightly during model calibration to achieve 

 optimal gating of sand across the boundary. 



369. Lines G.6 and G.7 . Geometrical properties defining the break- 

 waters are conveniently taken from aerial photographs. 



370. Line G.9 . The breakwaters are of standard layered rubble-mound 

 design (SPM 1984) and nongrouted; therefore, they are expected to be somewhat 

 permeable to incident waves. Also, during periods of high water levels and 

 high waves, wave transmission by overtopping will take place. The breakwaters 

 are expected to have relatively small values of transmission coefficients that 

 should be the same since the breakwaters were constructed of the same type of 

 stone and by the same procedure. However, the different water depths at the 

 breakwaters will change transmission properties, as will slight differences in 

 stone placement and structure settling. As an initial guess, the three 

 transmission coefficients are set to zero with the expectation that these 

 values will change. 



371. Line I . 1 . Beach fills were placed before as well as after the 

 simulation interval, but not between the dates of the shoreline (aerial) 



157 



