The annual rates of MSL shoreline migration and volume changes for 

 the three localities are summarized in Table 5. All profile lines at 

 Jupiter and Hollywood showed a net erosion, as indicated hy the MSL shore- 

 line position. However, one profile line at each of the two sites indica- 

 ted a net annual gain in beach volume. The net volume change at Jupiter 

 was a loss of 0.71 cubic yard per foot per year; the net change at Holly- 

 wood was essentially zero. The profile lines at Boca Raton, however, 

 indicated accretion, both by shoreline progradation and by beach volume. 

 The volume changes computed over this 4.5-year study are similar to those 

 computed by the U.S. Army, Corps of Engineers (1971) for a 26-year period 

 ending in 1955. 



Table 5. Rates of change on three southeast Florida beaches. 



Locality 



Profile line 



Change 



MSL shoreline 

 (ft/yr) 



Beach volume 



(yd3/ft/yr) 



Jupiter 



I 

 II 



-0.30 

 -0.42 



+0.53 

 -1.97 



Boca Raton 



I 



II 

 III 

 IV 



+2.08 

 +2.33 

 -0.37 

 + 1.84 



+0.34 

 -0.96 

 + 1.44 

 +0.76 



Hollywood 



I 

 II 



-3.48 

 -2.24 



-0.70 

 +0.79 



The magnitude of nearshore profile changes at Boca Raton was compara- 

 ble to the magnitude of the beach profile changes. However, the changes 

 on the two sections of the profiles were not directly related. Shore- 

 parallel reefs and the beach-rock ledge at and below the MLW line impede 

 the transfer of sand from the nearshore zone to the beach, but allow sand 

 to flow from the beach to the offshore zone. Neither the beach nor the 

 nearshore profiles provide conclusive evidence of migrating sand waves. 

 The presence of sand waves is suggested by changes on the two Hollywood 

 profile lines. 



4. Wave Statistics . 



Observations of breaker height and period made on a once-a-week basis 

 over the 4.5-year period resulted in the same average as observations 

 collected five times a week. 



Of the three methods used to record breaker direction, the method 

 allowing notation to the nearest degree was the most useful for predict- 

 ing longshore transport rates, although it probably overestimates the 

 frequency of waves approaching from 90° to the shoreline. 



100 



