the two profile lines between January 1969 and January 1973, was a shore- 

 line retreat o£ 0.4 foot per year which represented a volume loss rate of 

 0.71 cubic yard per lineal foot of beach per year. 



3. Boca Raton . 



Beach width on the four Boca Raton profile lines ranged from a mini- 

 mum of 80 feet (24.4 meters) (March 1971) to a maximum of 131 feet (39.9 

 meters) (April 1973). The average berm elevation was 7.6 feet (2.3 

 meters). The average monthly foreshore slope ranged from 9° to 14°, 

 with an overall average foreshore slope of 12° (1 on 4.7). The maximum 

 elevation change at any station was a loss of 7 feet (2.1 meters) at 

 pipe 4 (profile line II) between January 1970 and March 1971. This was 

 representative of a total loss of 9.20 cubic yards per foot (23.1 cubic 

 meters per meter) along the entire subaerial profile. 



a S hort-Temi Changes. Plots of the cumulative MSL shoreline and 

 volume changes are presented in Appendixes F and G. The changes are 

 referenced to the shoreline position and beach volume at the first sur- 

 vey. Profile lines I and II were established and first surveyed in Jan- 

 uary 1969; profile lines III and IV were not established and surveyed 

 until October 1969. A total of 1,002 sets of profile surveys was made 

 on the four Boca Raton profiles at an average of once each 1.5 days over 

 the study period. 



The average MSL shoreline change between surveys was 2.5 feet land- 

 ward or seaward. The average volumetric gain or loss when a change 

 occurred between surveys of the subaerial beach was 0.7 cubic yard per 

 foot (1.8 cubic meters per meter). Intervals which resulted in no meas- 

 urable net volume changes between surveys occurred about 35 percent of 

 the time. 



Similar to the beach changes at Jupiter, the more significant short- 

 term changes were generally associated with periods of high wave activity. 

 Changes associated with three specific storms are listed in Table 4. The 

 largest 24-hour loss was observed at profile line IV on 29 and 30 October 

 1969, when east and northeast winds at 25 miles (40 kilometers) per hour 

 and 6-foot breakers from the northeast were observed. This storm, which 

 closely followed the 24 and 25 October northeaster, caused a shoreline 

 retreat of 14 feet (4.3 meters) and volume loss equivalent to 3.3 cubic 

 yards per foot (8.3 cubic meters per meter) at profile line IV in the 

 24-hour interval. 



The largest 24-hour accretion (2.6 ciijic yards per foot, 6.5 ciobic 

 meters per meter) occurred on profile line II, between surveys on 26 and 

 27 October 1970. The shoreline progradation at profile line II was 5 

 feet during this same interval. Light westerly winds with breaker heights 

 of less than 0.5 foot (0.2 meter) (7.2-second period) on the 26th, in- 

 creasing to 2 feet (5.6-second period) on the 27th, were recorded. 



69 



