_Chonge in Shoreline Position 

 7 



New Profile (tg) 

 -40ft 



-Sediment Lost as Profile Retreats (t-t) 



Initial Profile (t. ) 



Sea^Level Rise 

 '^^— t. 



(Seaward Limit, tp ) ,. , 



It^ j 



Figure 72. Schematic of apparent sediment loss volume as the shoreline 

 retreats or sea level rises, t^ is beginning time and t 

 is end time. ^ 



(slope) (Everts, 1978). Two profiles, which were composites of nine shore- 

 normal profiles each, were taken 10 miles north of the study area (Atlantic 

 City) and 10 miles south (Wildwood) . Each of the profiles represents the 

 average profile at the location, and visible changes in slope appear at 35- 

 to 45-foot depths, an average of 40 feet. If -40 feet is assumed to be the 

 effective seaward limit of sediment transport, the apparent sediment loss above 

 MSL caused by a sea level rise at Ludlam Beach would be 0.75 cubic yard per 

 foot-year or 23,000 cubic yards per year for the entire island coast. 



5 . Beach Surveys . 



An important question in a beach study is when (time of year and frequency) 

 and where (profile line spacing) to survey a beach to produce useful results 

 A survey program, of course, depends on how the survey data will be used For 

 the type of results discussed in this report, the following guidelines are 

 given to assist m planning other beach survey programs. 



.a- Seasonal Considerations . A winter or spring survey will generally 

 indicate less sand on the beaches than in the summer or fall (Fig. 33) The 

 range of change between seasons is usually 2 to 20 times as great as the net 

 yearly change. The average for Ludlam Beach was 16 times as great. Thus the 

 time of year the surveys are made is very important because seasonal changes can 

 easily mask longer term changes. The survey program at Ludlam Beach indicates 

 that 3 years of monthly surveys is required to determine the average seasonal 

 change m sand volume on a beach. It must be noted that changes for a given 

 year do not always follow the average seasonal trend, nor are they the same the 

 length of the coast (Fig. 36). At Ludlam Beach the monthly change in beach 

 volume deviated significantly from the island average in the Sea Isle City 

 groins and at the south end of the island. 



94 



