Landward Boundary 

 Survey A 



H AS 



Unit Distance Parallel 

 to Shore 



Figure 26. Change in unit storage volume at profile line, AV. 



intensity. Seventeen storms, predominantly northeasters, were selected for 

 analysis based on the following criteria (see Table 5) : 



(1) Existence of prestorm surveys no more than 4 weeks before 

 the storm and poststorm surveys no more than 1 week after the storm; 



(2) data indicating wave heights of 1.22 meters or greater dur- 

 ing the storm (this value was arbitrarily chosen due to the 0.85- 

 meter value for mean wave height determined by Thompson and Harris, 

 1972); and 



(3) no other known significant weather events occurring between 

 surveys. 



Visual observations indicate that the predominant breaking wave directions 

 during storms are from the east and southeast. Wave breaker types most com- 

 monly observed were either plunging or spilling (Urban and Galvin, 1969) . 

 Analysis of the selected storms for which actual tide data were available 

 demonstrated an average maximum storm-generated surge at high water of 0.57 

 meter. 



An effect which must be considered is the timelag between the storm and 

 the poststorm survey which varies from to 6 days. The greater the lag, the 

 more probable that the beach has already begun recovering, thereby not indi- 

 cating the total storm change (Birkeraeier, 1979). (See App. C for plots of 

 prestorm and poststorm surveys. ) 



Figure 27 depicts the mean and standard deviation of unit volume changes 

 above MSL, by profile, for the selected storms. Due to the relatively few 

 storms analyzed, this information provides only a possible trend of unit 

 volume changes at each profile line. Profile lines 2, 5, 6, and 7 underwent 

 the greatest average unit volume loss of 6 cubic meters per meter or greater 

 during these storms. This is partly explained by the fact that the general 

 direction of longshore transport during storms is from northeast to southwest 

 in this area. Consequently, profile lines 2 and 5 are in littorally depleted 

 locations as a result of updrift groins and other manmade obstructions to lit- 

 toral drift (see Fig. 3). However, profile lines 6 and 7 are on relatively 

 unobstructed beach, so their changes in unit volume are presumably due to 

 onshore-offshore sand movement, or possibly movement downshore into the unsur- 

 veyed part of Absecon Island. 



The wide deviation at profile line 1 is undoubtedly a direct consequence 

 of its location immediately downdrift of the Absecon Inlet jetty. Profile 

 line 4, on the other hand, indicates a zero average unit volume change in 



32 



