profile locations corresponded to those used for the beach surveys. Profile 
measurements were made at different times of year (e.g., the 1955 measurements 
were '"'Feb.-Sept.,'" 1963 - "Oct.," and 1965 - "Sept."'). It is not known what 
the normal variability of the profiles is,so comparisons must be interpreted 
with caution. The profile lines obtained from the Philadelphia District were 
integrated from the MSL position to about the -10-meter MLW contour in order 
to compare the change in offshore sand accumulation. The integration was car- 
ried out at 3-meter depth intervals in order to compare the variability at the 
shallow intermediate and deep region. The change in area under each profile 
line as well as the net area change over the interval were computed. During 
the interval 1955-63, half of the profiles gained sand while half showed no 
change (profile 69) or lost sand. Much of the gain over this interval took 
place in profiles 72 and 73. A detailed look at the profiles showed a series 
of offshore bars which were nearly in phase between 1963 and 1965 but which were 
displaced landward more than 120 meters in 1955. Since similar sand waves 
were in phase during all three profiles at other locations, it is probable 
that the displacement was caused by a systematic error in the measurement. 
Most of the variability in the other profile lines took place near the shore 
at depths of -2 meters MLW or less. It is possible that the large increase 
in offshore sand volume between 1955 and 1963 is the result of erosion from 
the beach during the March 1962 storm. 
Many of the profiles showed bars nearshore before grading smoothly at a 
slope of about 1:20 seaward to the -6-meter depth. The slope then abruptly 
decreased to about 1:200 or less. Offshore features with relief less than 
the contour interval of the bathymetric chart (6 feet) do not appear on the 
charts. Profile 58, however, shows three sand waves with wavelengths of 
about 700 meters and amplitudes of about 1.5 meters present and in phase in 
the 1963-65 profiles. Much of the feature was also apparent in 1955. 
Though a firm conclusion is not possible from these data, the offshore 
features, such as bars and shoals, at depths of 6 meters and beyond appear to 
be stable, suggesting that most of the variability in sand volume takes place 
in the shallow beach face at depths less than 3 meters. 
2.) Spatial: Variability. 
Longshore and onshore-offshore variations in beach morphology were examined 
to determine systematic spatial variability including effects due to the prox- 
imity of profile lines to shore protection structures. Total volume calculations 
are often used as an indicator of the direction and degree of beach erosion or 
accretion. Calculations based on these profiles are shown as volume changes 
above the MSL shoreline in Appendix D, and the method of calculation is ex- 
plained in Section 3. The amount of beach (sand) volume depends upon the off- 
shore distance to which the calculations extend. If the distance is short, 
the recorded changes may have occurred only in the berm while very long profiles 
may show no net change because onshore accretion is compensated by offshore 
erosion. The existence of nodal points in the profiles representing onshore- 
offshore sediment exchanges (e.g., Aubrey, 1979) emphasizes the importance of 
selecting the proper offshore distance for volume calculation, especially when 
comparing results between different profile lines. Since the eigenfunction 
analysis retains spatial covariance information, volume changes can be readily 
calculated to any offshore distance, with the nodal points well delineated. 
47 
