A16 



Results and Discussion 



Using input data (Table Al) derived from the 20- year WIS hindcast 

 (Table A2) and a 102 x 91 grid, the wave model REFDIF generated wave 

 characteristics within the Saco Bay grid. Square cells (152 m or 500 ft) on 

 each side) were chosen in order to resolve bathymetric features in Saco Bay. 

 Figure Al shows a portion of the REFDIF grid for the immediate area of 

 interest extending beyond the physical model study boundaries. Some of the 

 most prominent land features, the transects where model results were saved, 

 and the two jetties in the Saco River mouth, are depicted in Figure Al. 



The input boundary of the REFDIF model grid is along the first row 

 (offshore row along the y-axis), and is situated at about the 61-m (2(X)-ft) 

 water depth. The origin (cell (1,1)) is located at the northeast comer of the 

 model domain in such a way that the x-axis is directed nearly due west (point- 

 ing from offshore-to-shore) and the y-axis points almost due south. North is 

 nearly in the negative y direction. The overall REFDIF grid covered an area 

 much larger than the physical model study area in order to ensure that diffrac- 

 tive and sheltering effects due to land masses and bathymetry were adequately 

 modeled as well as to move any side boundary effects out of the study area. 

 For other details about model setup, consult "Modeling Issues, Procedures, and 

 Input," above. 



Three different analyses were used for the nearshore wave estimates in Saco 

 Bay. These included REFDIF numerical model predictions, refraction and 

 shoaling, and SneU's law estimates based on the linear wave theory for which 

 a model was specifically developed for this study, and smoothed REFDIF 

 predictions representing average results along the transects described earlier. 

 SneU law estimates based on linear theory were provided because physical • 

 model study personnel specifically requested information about the shoaling 

 and refraction coefficients in addition to the REFDIF model estimates. Since 

 it is not possible to separate shoaling and refraction from the predictions of the 

 REFDIF model, it was decided to develop a separate computer program to 

 generate these coefficients. For this purpose, linear wave theory was used for 

 computaUon of parameters for SneU's law formulas. Wave number was calcu- 

 lated by the Fade approximafion of the linear dispersion relation (Hunt 1979). 

 Actual wave condition (height, period, and direction) values in 

 Table Al were also used in this method. 



Two tidal datum values were considered; a 0.0-ft tidal datum corresponding 

 to mean low water (mlw), and a +2.7-m (+8.8-ft) fidal datimi for mean high 

 water (mhw) level. For the mhw case, input wave conditions (Table Al) were 

 expanded to include more wave periods (9 and 1 1 sec for the 45-deg incident 

 wave direction, and 3 and 13 sec for the 22.5-deg incident wave direction, 

 respectively). These additions were mainly for the northeasterly storm, which 

 may reach the wave generator location (in the physical model setup) since 

 wave energy may increase with an increase in water level (i.e., from 0.0 to 



Appendix A Saco Bay Nearshore Wave Estimates 



