Comparison of the results of this study with those of Jarrett's 

 (1977) are encouraging. Although Jarret calculated his /3 value based 

 only on the midsection of Wrightsville Beach, his value of 

 /3 = 418 m 3 -s/N-yr is approximately equal to the upper limit of the 

 value of /3 for Wrightsville Beach as predicted by this study. 



5 . Sediment Budget . 



To illustrate the application of the sediment transport model in 

 estimating the northerly and southerly longshore transport rates and the 

 quantity of material lost into the adjacent inlets, sediment budgets 

 using littoral cells of finite length along Wrightsville and Carolina 

 Beaches were performed. Each beach was divided into the three cells 

 which, as described in Section IV, 4, best represent the long-term 

 volumetric changes along those beaches. Losses from the active profile 

 due to a rise in sea level, losses from the beach due to inlet trapping, 

 and losses or gains in each cell due to longshore sediment transport 

 were all considered. The long-term excursion rates which were used to 

 determine the annual volumetric beach change for each cell were 

 calculated by eliminating identified excursions, both within the project 

 boundaries and along downdrift beaches, due to the placement and 

 subsequent initial erosion of beach fills. Consequently, the 

 contributions to, and the commensurate offshore losses from, the overall 

 sediment budget due to beach-fill operations were addressed and do not 

 need to be further incorporated into the sediment budget equations. 

 Aeolian losses were considered inconsequential (U.S. Army Engineer 

 District, Wilmington, 1977) and also were not included. An inherent 

 assumption within this approach to developing a sediment budget is that 

 offshore losses due to ongoing sorting of freshly exposed beach face is 

 minimal. This assumption is addressed later in Section VI and was found 

 to be valid. 



Based on the concept of maintenance of an equilibrium profile under 

 rising sea conditions (Bruun, 1962), the annual volumetric loss of 

 sediment due to a sea level rise is shown in Tables 6 and 17. Losses 

 due to wave overtopping occurred only along the northern section of 

 Carolina Beach. Aerial photos taken in May 1964 and November 19 74 were 

 used to estimate the bayward excursion of the bayside shoreline. 

 Results from that analysis indicated that approximately 4,600 m 3 /yr 

 was lost from the oceanside of Carolina Beach (U.S. Army Engineer 

 District, Wilmington, 1977). 



Table 17. Annual volumetric changes in beach— cell volume and losses 

 due to sea level rise and wave overtopping, 





Change in beach- 



Loss due to 



Loss due to 



Beach 



cell volume 



sea level rise 



wave overtopping 



cell 



(m 3 /yr) 



(m 3 /yr) 



(m 3 /yr) 



Wrightsville (north) 



-24,430 



2,289 







Wrightsville (central) 



-77,530 



1,873 



— 



Wrightsville (south) 



-12,370 



1,457 



— 



Carolina (north) 



+104,500 



700 



4,600 



Carolina (central) 



-269,750 



1,582 



— 



Carolina (south) 



-107,970 



2,285 



— 



78 



