meters per meter. The reason for the large difference between cell A and the 
two other cells is not known. Each cell shows a change in above MSL volume at 
the north side which is negative relative to the mean while the south side of 
the cell is less than the mean but positive in the two southern cells. The 
latter suggests net transport toward the south while cell A suggests a slight 
net transport toward the north. Rates of transport cannot be determined from 
the available data. This section of beach may be the site of a local nodal 
point in sand transport direction. Similar, closely spaced profile line studies 
in groin cells to the north, would be necessary to confirm this possibility. 
The variability in the change within each groin cell indicates that repeated 
measurements of single profile lines placed between adjacent closely spaced 
groins may not accurately reflect the change within that cell. Figure 28 indi- 
cates that profile lines located in the middle of a groin cell would show a 
net change greater than the mean, while profile lines near the groins would show 
a lesser or negative rate of change. At least three profile lines should be 
located within a groin cell in order to resolve the direction of net transport 
and amount of change. The distribution of change within a cell also implies 
that regression estimates of the rate of change in MSL shoreline or above MSL 
sand volume from the available data from other profile lines would not provide 
a meaningful indication of beach development. 
V. DISCUSSION 
1. Profile Changes. 
The profile lines along the Long Beach Island beaches are characterized 
by a high degree of variability that occurs on a number of time and space 
scales. The empirical eigenfunction analysis has shown (Fig. 22) that the 
variability generally increases from the north end of the island, which has 
been stabilized by the Barnegat Inlet jetties, toward the unstructured Beach 
Haven Inlet. The profile lines between these two extremes have, with the 
exception of the groin field studies, been placed along the beach with little 
regard for proximity or relationship to the groins. The beach variability 
prior to groin construction is unknown so it is not possible to assess the 
effect the structures have had on this factor. A long-term study on an un- 
structured beach in a similar environmental setting would provide a useful 
contrast of processes. Island Beach State Park, north of Barnegat Inlet, may 
provide a reasonable candidate site for a comparative study. 
The erosion or accretion rate of the Long Beach Island shoreline remains 
unresolved. Linear regression analysis was used on profile lines 1 to 21 to 
estimate the rate and direction of change in the MSL shoreline position. A111 
except five of the profile lines (7, 8, 9, 11, 21) showed a positive correla- 
tion between the MSL shoreline and time. The mean accretion rate of 0.56 
meter per year indicates that the beaches along the island are building sea- 
ward even in the period of long-term sea level rise. The method of Weggel 
(1979) was used to estimate the expected erosion rate caused by the latter. 
This estimate is 0.68 meter per year. Both of these must be treated with 
caution since they are based on assumptions that may not be valid for the Long 
Beach Island system. 
55 
