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SECURITY CLASSIFICATION OF THIS PAGE(1Rian Datm Bnland) 



current directions were observed to change seasonally, with directions from 

 the northeast dominating during October through March and from the southeast 

 during April through September. Potential gross longshore transport rates, 

 estimated from these data, ranged from 1,800,000 cubic meters per year at 

 Jupiter to 1,200,000 cubic meters per year at Boca Raton, to 480,000 cubic 

 meters per year at Hollywood. The magnitude of beach changes, as defined by 

 shoreline position and sand volume on the beach, decreased from north to south 

 and is relatively low compared with typical U. S. east coast beaches. 

 Contributing factors include the sheltering effect of the Bahama Banks, the 

 lack of significant storms, and the underlying coquina limestone which 

 characteristically crops out just below the MSL shoreline, forming a protec- 

 tive reef that effectively retards erosion. Beach changes were seasonal in 

 nature, but were reversed at Boca Raton, where beach width and sand volume 

 were highest during the winter months. Seasonal beach changes were two to 

 three times greater than year-to-year changes. The average unit volume 

 change rate above MSL was -1.8 cubic meters per meter per year at Jupiter, 

 +1.0 cubic meter per meter per year at Boca Raton, and +0.1 cubic meter per 

 meter per year at Hollywood. Corresponding MSL shoreline migration rates 

 were -0.1 meter per year at Jupiter, +0.46 meter per year at Boca Raton, and 

 -0.9 meter per year at Hollywood. Nearshore volume changes between surveys at 

 Boca Raton were not related to above MSL beach changes. 



UNCLASSIFIED 



SECURITY CLASSIFICATION OF THIS PAGEfWhO" D«(a Entared) 



