c. Yearly Changes. A notable year-to-year variation in sand volume above 

 MSL and in shoreline position was measured on Ludlam Beach (Fig. 37). Yearly 

 changes varied from a gain of 2.9 cubic yards per foot between 1964 and 1965 

 to a decrease of 4.6 cubic yards per foot from 1966 to 1967. This corresponds 

 to the net 100,000 cubic yards gained at Ludlam Beach in 1965 and the 160,000 

 cubic yards lost in 1967. An unknown part of the 1965 volume increase resulted 

 from a dune rebuilding program after a September 1964 storm. The cumulative 

 sand volume from 1962 to 1972, and referenced to zero in 1962, is illustrated 

 as a solid line on the figure. 



7.5 



': ^-^ 



i 

 ;.-2.5 



;-5.0 

 -75 



/ 



A 



Cumulative 

 Volume 



V 





- 





/ 





\ 







/' 



-V 











\ 



V 





A 



\ 













X 







\/ ' 









\ 















I 





1 



\" 



1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 

 (Yr) 



7.5 



5.0 5 



>-. 



2.5 t 



O 



> 



-o 



c: 

 o 

 to 



-2.5?; 



-I- 

 o 



-5.0 i 



7.5 



Figure 37. Yearly volume change and cumulative volume 

 above MSL at Ludlam Beach, showing extreme 

 variability between years. 



Changes in the MSL shoreline intercept were similar to yearly changes in 

 sand volume above MSL. Figure 38 shows the shoreline position change between 

 years and the cumulative shoreline change over the 10-year study period. 

 (Shoreline position was computed by weighting by distance between profile 

 lines; the MSL shoreline position obtained from each profile line for each 

 survey, then averaging the survey averages for a given year.) Between years, 

 the maximum shoreline retreat was 23 feet. The maximum yearly progradation 

 was 16 feet. 



d. Net 10-Year Change . The average long-term rate of sand loss was 1.12 

 cubic yards per foot-year as determined by a linear regression fit to the cumu- 

 lative volume line (Fig. 39). The equation of the regression line is 



Vy = -1.12(Y 



1962) + 5.8 



(1) 



51 



