WB36, the approximate start of the alinement problem. Between 1965 and 

 1970, the beach on the north side of the Masonboro Inlet jetty accreted, 

 however, the central island bulge and alinement problem remained. The 

 1970 beach fill was placed approximately between arrows A and A' , thus 

 reinforcing the beach alinement problems. The greater relative change 

 in beach planform and nearshore bathymetry in the central section of the 

 island from 1965 to 1975 resulted in higher wave activity and erosional 

 trends . 



Natural beach processes tend to focus on and smooth out irregular- 

 ities, thus creating a smoothly curving beach as is idealized by the 

 dashline in Figure 45. The high rates of erosion and initial losses 

 associated with the 1970 beach fill may not be typical of all beach 

 fills, but may have been partly caused by the exposure to increased wave 

 attack due to the misalinement of the beach planform. The resulting 

 implication means that if improvement in performance of a future 

 beach fill located in the same area is desired, then additional fill 

 should be placed along the adjacent beaches, as shown by the dot-dash 

 line in Figure 45, to remove the alinement problem. This, however, may 

 not be an economically feasible solution. 



Information obtained from the postfill beach response was used to 

 examine the assumption in the sediment budget analysis that offshore 

 losses due to sorting of freshly exposed beach material were minor. 

 Equation (6) showed that 4.06 years after the fill placement, the beach 

 returned to its prefill position and with approximately the same near- 

 shore profile (Fig. 44). This means that whatever came into the fill 

 area during the 4.06-year period was transported out by the end of that 

 time. 



The sources of sediment include longshore transport into the fill 

 region, material placed during the beach-fill operations, and material 

 brought ashore by seasonal onshore transport. Losses of sediment 

 include longshore transport out of the fill region, losses due to 

 sorting of the beach fill, seasonal losses due to offshore transport, 

 losses due to the rising sea level, overwash, and aeolian processes. 

 Since the pre- and end-of-period profiles had approximately the same 

 shape, the net volumetric changes due to slope readjustment were zero. 

 Over an even 4-year period, seasonal changes should approximately 

 balance out, and so within the limits of accuracy of this study, the net 

 on/offshore contribution was set to zero. Volumetric gains from the 

 beach fill (BF) were determined from surveys, and associated sorting 

 losses (sorting) were calculated using the adjusted fill factor 

 (R^). Losses due to sea level (SL) were calculated by use of 

 Bruun's (1962) formulation. Aeolian and washover losses were near zero. 

 Since the net volume change at the end of the 4.06-year period was zero, 

 then the net volumetric change due to alongshore transport of the 

 boundaries (Qi n ~Qout^ mu st equal the difference between these 

 identified sources and sinks since the fill area was away from active 

 inlets, jetties, etc.; i.e., 



Qin " Qout + BF - sorting - SL = 

 Qin " Qout + BF/R A - SL = 



89 



