Calculation results at R-7 for the three selected storms, with the final profile position as post- 

 TS Gordon, are shown in Figure 3-8. The storms caused substantial erosion on the upper beach. 

 Specifically, as listed in Table 3-5, the MHW shoreline receded approximately 15 ft during the 

 Thanksgiving Day storm, 31 ft during the March 1989 northeaster, and 24 ft during the 1994 

 Tropical Storm Gordon. The SBEACH model produced some washover, which is the landward 

 transport of sand. 



Table 3-5 summarizes both the MHWL recession and maximum net loss of beach and dune 

 volume landward of the location of the MHWL in the units of cubic yards per foot (cy/ft) of 

 beach alongshore. Offshore sand transport rates ranged between 10.8 and 11.9 cy/ft. Using the 

 conversion that 1 cy/ft = 2.5 cu m/m, the maximum transport rates fall in the range of 27 to 

 29.8 cu m/m of berm crest. These rates are in the midrange of storm-induced beach and dune- 

 erosion rates as documented by Savage and Birkemeier (1987) measured for 13 storms at several 

 northeastern beaches of the United States facing the Atlantic Ocean. It is noted that the 

 calculated beach and dune erosion and recession corresponds to a profile that is not armored. 

 Such would have been the case for the fill placed along the beach in 1974/75. The cumulative 

 eroded volume from the storms is calculated as (1 1.9+1 1.3+10.8 cy/ft) x 106 ft = 3,600 cy. 



12 



Initial 07/83 



200 



Thanks 11/84 



NE 03/89 



Gordon 11/94 



MHW 



250 



450 



300 350 400 



Distance Offshore, ft 

 Figure 3-8. R-7: Beach recession by three selected recent storms. 



500 



3-18 



Chapter 3 Assessment of Coastal Change 



