Survey B 



VA^ 



SUBAERIAL UNIT 

 VOLUME ^ ,,p7 

 CHANGE " ^'^ 



lydVft] 



Cross-Sectionol 



Area Change 



Between Surveys AandB 



Ift2] 



X 



Unit Distance 

 Parallel to 

 Shore 

 (1 ft) 



Figure 22. Definition of MSL shoreline change and 

 subaerial unit volume change. 



III. RESULTS: LITTORAL ENVIRONMENT OBSERVATIONS 



1. Statistical Significance . 



Littoral environment observations and sand height were measured once 

 a week at Jupiter (Thursday) and Hollyivood (Tuesday) , and five times a 

 week (Monday to Friday) at Boca Raton. In analyzing these data, several 

 points must be considered relative to the frequency of data collection 

 at each site and the statistical significance of the length of the study. 

 First, there is the problem of comparing or relating data which have been 

 taken once a week (Hollywood and Jupiter) to data taken five times a week 

 (Boca Raton) . Certain apparent differences in the three sites may be 

 attributable to insufficient data from either Hollywood or Jupiter. To 

 test the statistical significance of once-a-week versus five-times-a-week 

 sampling, a comparison was made between the set of daily breaker height 

 and period data collected at Boca Raton and a once-a-week sample from that 

 same data set. To simulate the sampling plan at Jupiter and Hollywood, a 

 subs ample which included every Wednesday observation was selected from the 

 Boca Raton data. If no Wednesday observation was made, the closest obser- 

 vation day was selected. This test resulted in a subs ample of 229 obser- 

 vations out of a total sample of 1,077 observations. The average annual 

 breaker height from both the total sample and the subsample was 2.0 feet, 

 with a standard deviation of 1.4. Average breaker period from both the 



38 



