resolution in the Oregon Inlet vicinity was modified to relax stability 

 exigencies, economize simulations, and yet preserve major inlet features. 

 Final adjustments of boundary conditions and friction characteristics were 

 performed using a tidal period of 19-22 May 1975 which is coincident with data 

 from the previous physical model study (Hollyfield, McCoy, and Seabergh 1983) 

 of Oregon Inlet. 



36. Marigrams presenting model versus prototype M amplitudes appear in 

 Plates 7-10 starting at 0300 (GMT) 20 Mav 1975. The model quite accurately 

 reproduces the open-coast tide as observed at all available stations. Model 

 performance at Oregon Inlet is characterized by good agreement at Bonner 

 Bridge and the Pea Island Coast Guard Station. The remaining stations present 

 comparisons at bayside locations in the inlet vicinity. They also show good 

 agreement with amplitude variances less than 0.1 ft and some flight phase 

 shifting attributed to channel and shoal features subscale to grid resolution. 



Shore Process Model 



37. Unlike the coarser models used in the study, the shore process 



model presented a unique case for calibration. Open-boundary conditions were 



not adjustable since they were transferred from simulations on the nearshore 



model. Because the primary function of this model was to provide hydrodynamics 



for sediment transport studies, cell depth changes were restricted in order 



to maintain the same bathymetry for these two modeling efforts. Friction 



values were adjusted to coincide with representations in the nearshore model. 



The inclusion of the momentum advection terms and the very fine grid resolution 



(Ax . = 100 ft) with the resultant small time-step (At < 15 sec) required 

 min — 



careful adjustments of the eddy viscosity coefficient to achieve simulation 

 stability, and yet produce realistic circulation currents and horizontal 

 eddies evident at the inlet under normal and proposed configurations. Cali- 

 bration efforts for this model were performed for mean tides produced by 

 nearshore model simulations in the aforementioned May 1975 period. Results 

 are discussed in PART V, and model gage locations are shown in Figure 8. 



26 



