b. Yearly Considerations . Yearly changes in sand volxime naist also be 

 considered when planning a survey program. On Ludlam Beach the net long-term 

 change was -1.12 cubic yards per foot, but changes between years, both accretion 

 and erosion, averaged twice that, and in some cases were four times greater (Fig. 

 37). 



When planning a program for determining the net change in beach volume, a . 

 number of yearly records are needed. It should be noted that the migration 

 of a sand wave past a specific beach site takes 10 to 11 years. Net volume 

 change data obtained from surveys of less than a 10-year period would be biased 

 by the sand wave. 



c. Survey Frequency . As stated, a minimum of 10 years of survey data is 

 needed to obtain a net yearly volume change rate. To obtain consistent data, 

 surveys should be made on the same profile lines at the same time each year. 

 Two surveys per year would probably be sufficient. The best times to survey 

 are during intervals when the beach is not changing rapidly (Fig. 33) : February 

 to May (the seasonal volume minimum) , when losses have stopped but material gen- 

 erally has not moved inshore above MSL, and July and August (the seasonal volume 

 maximum), when winter storms have "not, in general, removed too much sand from 

 the beaches. Between these times the beaches above MSL are either rapidly 

 gaining or losing sand. 



d. Sand Waves . The possibility of migrating accretional features, up to 

 10 or 11 years past the time they began, should be considered when using beach 

 surveys to determine changes in beach volume or shoreline position. Sand waves 

 appear to occur after an event causes a large volume of beach sediment to accu- 

 mulate on the updrift end of a barrier island. If such an event is suspected 

 the presence of sand waves should be anticipated. The sand volume change 

 caused by a migrating sand wave averaged 15 to 20 cubic yards per foot between 

 the wave crest and trough on Ludlam Beach. 



e. Profile Line Spacing . To determine the net yearly volume change on 

 Ludlam Beach, away from the inlet and groin systems, a spacing of 2,000 to 3,000 

 feet was enough to pick up the alongshore trend in erosion or accretion. At the 

 inlets a closer spacing of perhaps 1,000 feet is warranted. Within groin systems 

 a profile line in the center of each groin compartment appears to be the least 

 that will provide representative net long-term beach change data. The same 

 spacings appear to be sufficient to determine seasonal changes (Fig. 33) . 



Trends of beach volume changes, when averaged for seven storms (Fig. 32), 

 were not consistent in the indentations north and south of the Sea Isle City 

 groins. This was especially true north of the groins. The spacing required 

 to pick up these trends is unknown. 



f. Volume Versus Shoreline Changes . In general, the beach volume above 

 MSL is directly related to the position of the shoreline. In some instances, 

 however, a progradation of the MSL shoreline occurs when the upper foreshore 

 erodes. This condition has been observed, for example, after storms on Long 

 Island (Everts, 1973) and at other east coast localities (DeWall, Pritchett, and 

 Galvin, 1977; Birkemeier, 1979). Caution in interpreting beach volume change 

 from shoreline position change on aerial photos is therefore suggested. 



g. Offshore Surveys . Offshore surveys were not routinely made during the 

 course of this study. However, the offshore should be surveyed, if possible, 

 to account for the total sand budget. This is especially true in describing 

 onshore-offshore movements of beach sand. 



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