70° 53.5' W (Figure 24). This puts the Phase III station approximately 4.6 mi 

 due east of Roughans Point in 75 ft of water. Cape Ann, to the northeast, and 

 Cape Cod, to the southeast, provided some shelter for the Phase III station. 



The sheltering was such that only those waves approaching from between M40° E 

 and S60° E could reach the Phase III station. 



49. Phase III results were produced at 3-hour intervals. Linear 

 interpolation was used to calculate H , f , e , H m , f m , and e for 

 every hour. 



Wave Climate Simulations for Broad Sound 



Summary of ESCUBED 



50. The reader is referred to Hubertz (1985) for a detailed discussion 

 of ESCUBED. Relevant aspects of the model are presented here. 



51. Essentially, ESCUBED propagates components of discrete directional 

 spectra over a user specified bathymetry. Calculations proceed to propagate 

 individual components of these spectra across a rectangular, uniformly spaced 

 finite difference grid. 



52. The grid used for the wave climate simulations at Broad Sound is 

 shown in Figure 24. The grid spacing in both the x and y directions is 656 ft 

 (200 m) . At each grid point, the energy of the individual components of a 

 spectrum is limited by the finite depth water equilibrium range proposed by 

 Kitaigorodskii, Krasitskii, and Zaslavakii (1975). The range, which applies 

 for frequencies greater than the peak, is a function of depth and frequency. 

 This limitation could be thought of as an energy sink where the energy loss is 

 through turbulent and viscous processes associated with white capping and 

 large scale breaking. 



Determination of a spectrum 



for the ESCUBED boundary condition 



53. The Phase III wave characteristics for sea, R. , and f_ were 



o 

 used to generate a TMA spectrum E TMft (f,h) (Hughes 1984). The TMA spectrum 



is representative of fully developed wind seas in finite depth water. 



54. The TMA spectrum was evaluated using the depth at the Phase III 

 station, i.e. h = 75 ft . Let E TMA (f,75 ft) = E TMA (f) . The one- 

 dimensional spectrum ErpM/\(f) was distributed directionally using a 



cos (9 - 9 ) spreading. No energy was allowed to have a direction outside 



42 



