volumetric erosion expected to occur on 75 percent of the shoreline. The so- 
defined variability factor was determined to have the value 2.0. Assuming 
that the results computed in the present study are median values, multipli- 
cation by the factor 2.0 would encompass 75 percent of the expected recession 
of the shoreline. It should be noted that the data set compiled by Savage and 
Birkemeier does not include events greater than the 100-year storm. 
177. There are limited data available for the project site with which 
to test the variability concept. Caldwell (1959) provides average and maxi- 
mum values of landward retreat of selected contours above MLW for the New 
Jersey Storm of 6-7 November 1953 (Table 9). A total of 20 profiles spaced 
over approximately 40 miles of the north New Jersey coast were averaged in 
the comparison, omitting measurements which were believed to be influenced 
by the presence of the seawall. This information is a good source with which 
to examine longshore variability in recession at the site (subject to consi- 
derations of storm sequence given in the next paragraph). Data presented in 
Table 9 are compatible with a variability factor of 2.0 as discussed above. 
178. There is an ambiguity associated with the data given in Table 9. 
As discussed above, at least one other storm is known to have impacted the 
area in the interval between profile surveys. Caldwell (1959) takes note of 
this and states "... it is believed that the greater part of the indicated 
erosion took place during the (6-7 November 1953) storm itself." 
179. The methodology and recommendations given here were developed to 
estimate beach erosion resulting from a single event. A natural shore exper- 
iences several annual erosive events of various strengths, continual shoreline 
evolution caused by longshore sediment transport, and accretion under summer 
swell conditions. Given the long-term trend of the project coast to erode, 
consideration of multiple erosive events and natural longshore variability 
indicate that a variability factor on the order of 2.0 should be incorporated 
in the protective berm design. 
180. Incorporation of the variability factor is made by determining the 
frequency of occurrence of maximum recession equivalent to one-half the design 
berm width. This approach gives a conservative estimate of the minimum recur- 
rence interval for complete erosion of the flat portion of the design berm. 
Initial computed recession values can not be doubled for the variability 
analysis because recession is limited by the presence of the seawall; con- 
tinued erosion beyond the design width would result in scour at the face of 
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