u 2 f. - ;j Af < f < f. + tj Ai 



H . 1 d. 1 d. 



and 



3me ...h.<»<..4.. 



otherwise 



Finally, the discrete directional spectrum used as a boundary condition for 

 ESCUBED is the sum of E sea ( f i » 9 i ) and E swe ll (f i' e i ) • 



ESCUBED Results 



57. ESCUBED output contains the following information from the wave 

 climate simulations: 



a. H_ , f m , and 9 representing the energy based significant 



wave height, the frequency of the spectral peak, and the di- 

 rection of the spectral peak at each grid point, respectively. 



b. Directional and one-dimensional spectra at selected points in 

 the vicinity of Roughans Point and at points 1.24 miles due 

 east of Roughans Point. 



Model results in the lee of Nahant Peninsula indicated that, in this area, 

 ESCUBED inadequately simulated the local wave generation by wind. Although 

 ESCUBED allowed wind energy to be added to the energy of existing waves, 

 ESCUBED did not allow initial growth of waves in the areas sheltered from the 

 WIS input on the boundary. Since these locally generated waves are especially 

 important for waves at the north wall of Roughans Point and for locations 

 along the shore of Broad Sound from Point of Pines into Lynn Harbor, further 

 analysis was required. 



Locally Generated Waves in the Lee of Nahant Peninsula 



58. The equations for shallow-water wave growth for fetch-limited 

 waves, presented in the Shore Protection Manual (SPM 1984, p. 3-55), were used 

 to obtain an improved determination of the waves attacking the north wall at 

 Roughans Point, at Point of Pines, and at locations in Lynn Harbor. 



59. The depth and fetch vary across Broad Sound. At each point where 

 the locally generated analysis was required (see Figure 25 for locations 

 marked A-E), the area was divided into sectors as shown in Figure 26 for the 



44 



