where V^ is the mean sand volume loss or gain (in cubic yards per foot-year) 

 since 1962, based on the linear regression computation, and Y is the year. 

 Note the small net annual erosion rate when compared to the wider fluctuations 

 which occur seasonally (Fig. 33) and as a result of storms (Fig. 32). The 

 correlation coefficient for equation (1) is -0.88. Thus, 77 percent of the 

 variation in mean yearly volume change is accounted for by the linear relation- 

 ship in different years. Everts, DeWall, and Czerniak (1974) obtained a mean 

 yearly sand loss rate about twice as great for the beach at Atlantic City (2.1 

 cubic yards per foot -year) . 



Large variations in the mean yearly volume change along the length of 

 Ludlam Beach (Fig. 39) ranged from a net loss of -6.8 cubic yards per foot- 

 year at Corson Inlet to a gain of +3.3 cubic yards per foot -year at the north- 

 ern part of the Sea Isle City groins. The area near Townsend Inlet was nearly 

 stable while the indentations between the inlets and the Sea Isle City groins 

 experienced loss rates averaging -2 to r-3 cubic yards per year-foot. 



5. Alongshore Redistribution of Beach Material . 



The mean change in yearly sand volume and shoreline position on Ludlam 

 Beach was not similar (Figs. 40 and 41). Sand volume increased and decreased 

 in a time-ordered sequence from north to south during the 10-year study. 

 Periods of shoreline advance alternated with periods of shoreline retreat, 

 and volume changes indicated beach material moved alongshore and above MSL 

 in "humps" or waves. This movement, in a time-ordered sequence, is plotted 

 by a visual fit on the figures. A solid line indicates the movement through 

 time, from north to south, of a volume maximum or hump. Dashlines indicate 

 the progressive southward shift of the volume minimum (yearly mean loss). 

 The dotted lines follow the yearly position of the zone of approximately 

 no volume change along the coast. Note that the interval between each 

 profile line histogram on Figures 40 and 41 is not plotted to scale. This, 

 however, does not mask the alongshore distribution of the volume or shoreline 

 trends through time. It does allow the histograms to be fitted on the figures, 

 The yearly change in shoreline position and sand volume is largest at profile 

 lines near Corson Inlet. 



6. Profile Envelopes . 



Profile envelopes are bounds, which enclose the maximum measured profile 

 variations for each profile line, and are the upper and lower limits of change 

 experienced by a beach profile for a finite number of surveys during a specified 

 time interval. When plotted, the data provide an easy means of determining the 

 lower and upper profile extremes, and the landward bound for elevation and con- 

 tour intercept changes. The plots may also indicate accretion or erosion trends. 



53 



