2. Long-Term Changes . 



Long-term changes include the cyclic seasonal changes (U.S. Army, Corps of 

 Engineers, Coastal Engineering Research Center, 1977) along with longer range 

 trends which may or may not be cyclic in nature. Changes in the MSL shoreline 

 position during 1962-73 are shown in Figure 44. The 1963 and 1970 beach fills 

 are evident on profile lines 1, 2, and 3 with subsequent progradation on the 

 downdrift profiles, which was also shown in the unit volume changes (Fig. 

 33). Figure 45 depicts the average unit volume and MSL shoreline position by 

 month for each of the profile lines. The mean of the monthly averages for 

 each profile is indicated by the "zero" unit volume, whereas the "zero" MSL 

 shoreline position is the shoreline position during the first survey. Figure 

 45 shows that seasonal changes do occur at Atlantic City, with the least vol- 

 ume of sand on the beach from January to March and the greatest volume of sand 

 generally from June to August. This large quantity of sand also appears pre- 

 dominantly on profile lines 1, 2, and 3 with profile lines 5, 6, and 7 showing 

 a loss of sand during June and July. These extremely large volumes at profile 

 lines 1, 2, and 3 predominantly reflect the beach fill of 1963 in which 'the 

 bulk of the fill material was placed along these profile lines as shown in 

 Figure 32. These values may also be misleading since only four surveys were 

 conducted in June and two in July throughout the 11-year study period, with 

 each of the profile lines surveyed twice during June, July, and August of 1963 

 after the 1963 beach fill. June and July were the least surveyed months 

 during the study period (Fig. 21). In addition, all profile lines were sur- 

 veyed in August 1970 after the 1970 beach fill, thereby adding a bias to the 

 six surveys conducted in August throughout the study. Therefore, the infor- 

 mation for these months is less representative of average summer conditions. 



To evalute the entire Atlantic City locality as a whole, AS and AV 

 were averaged by year in the alongshore direction. The averaged alongshore 

 change in MSL shoreline, AS, is computed by summing the alongshore distance- 

 weighted yearly average values of AS at each profile line and dividing by 

 the total length of the study area. Similarly, the averaged alongshore change 

 in storage volume, AV, is computed using the alongshore distance-weighted 

 values of AV (Czerniak, 1974). 



A comparison of the mean yearly changes in storage volume and MSL shore- 

 line (Fig. 46) shows that the long-term trends are influenced more by the 

 magnitude of the accretion-erosion and progression-recession occurring in 

 these years than by the number of net accretionary or erosional years. This 

 is clearly indicated by the high dependency on the two artificial beach fills 

 in 1963 and 1970 for the shape of the cumulative yearly change in storage 

 volume, AV (Fig. 46). In conjunction with this, yearly changes in the MSL 

 shoreline and storage volume vary considerably and appear to suggest no clear 

 pattern. 



Figure 47 shows the changes in unit volume and shoreline position for the 

 years between the beach nourishment projects in 1963 and 1970. The slope of a 

 least square fit line drawn through the points on the plot of cumulative aver- 

 age yearly change in storage volume for the seven profile lines (Fig. 47) 

 provides a single number which best describes the rate of "natural" change in 

 the above MSL storage volume during this period. The line only provides a 

 general description of the trend in the data due to the wide yearly variation 



45 



