Some of the profiles which are surveyed frequently must be surveyed 

 out beyond the MLW position to approximately the position of the 

 -10 meter contour. These long profiles are necessary to establish the 

 actual volumetric changes for the entire active profile, and hence, used 

 to calculate the volumetric equivalent factor applied to the intermediate 

 profiles . 



If the seasonal variation in beach excursion is larger than the 

 long-term trends, then profile data must be collected for a minimum of 2 

 to 3 years for both processes to be quantified. Greater variability in 

 the data necessitates longer collection periods. 



For projects with tight budget constraints, a few profiles located 

 in key positions and surveyed frequently will provide a better data base 

 than more profiles surveyed infrequently. 



Wave gage data collected at Johnnie Mercer's Pier and LEO data from 

 Wrightsville Beach were combined to develop a wave climate representa- 

 tive of the wave conditions found along the study area. This data was 

 refracted in to shore and the breaking wave conditions were used to 

 calculate both the northerly and southerly components of longshore 

 energy flux. The spatial gradient of these values along Wrightsville 

 and Carolina Beaches were compared with the long-term (nonseasonal) 

 volumetric changes, and the empirical factor, /3 , which relates the 

 longshore sediment transport rate to the longshore component of energy 

 flux was calculated. By choosing a best-fit value of /3 =300 and 

 j3 =900 m-*-s/N-yr for Wrightsville and Carolina Beaches, respectively, 

 plots of predicted and measured volumetric change due to longshore 

 sediment transport along each beach showed similar trends, although the 

 absolute magnitude at any beach location was different. 



To improve the accuracy of the energy flux computation in future 

 studies, the following recommendations on desirable refraction model 

 characteristics should be utilized or developed. 



(a) Variable grid cell spacing should be used to allow coarse-sized 

 computational cells in deep water and finer cells in the 

 nearshore region where greater relative changes in bathymetry 

 can cause instability problems. 



(b) The effects of diffraction and tidal currents on wave 

 propagation should be included. 



(c) The dynamic interrelationship between both the nearshore 

 bathymetry and shoreline planform, and the sediment transport 

 potential of the incoming waves should be incorporated. The 

 present static boundary condition representation of the shore- 

 line, used in refraction analysis programs, does not allow for 

 any change in shape in the shoreline due to increased sediment 

 transport capabilities as a result of increased (focused) wave 

 activity. Thus changes in refraction patterns and beach 

 approach angles due to beach response between different sets of 

 wave types used to represent seasonal or annual conditions 

 should be included. 



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