coast, extending from Duval County at the north to Dade County at the 

 south, were examined and proposed project requirements summarized by 

 Duane (1968). The projects showed an initial fill requirement of some 

 26 million cubic yards of material with annual replenishment of slightly 

 less than 2 million cubic yards. Over a 50-year maintenance period, 110 

 million cubic yards would be required. 



Corps of Engineers studies prepared for specific beach erosion control 

 projects in Palm Beach, Broward, and Dade Counties estimate requirements 

 of nearly 21.5 million cubic yards of sand for initial fill and maintenance 

 requirements of nearly 900,000 cubic yards annually. Thus, for a 50-year 

 economic life, an additional need of approximately 45 million yards of 

 sand can be forecast. Requirements for specific coastal sections within 

 the limits of this study area are summarized in Table II- 



Using erosion and shoaling data from Beach Erosion Control reports. 

 Watts (1962) estimated that an annual net of 842,000 cubic yards of sedi- 

 ment had eroded shoreward of -18 feet MLW between Lake Worth Inlet and 

 Government Cut (Miami) for at least 30 years prior to that report. The 

 annual loss into inlets during this period was estimated at 200,000 cubic 

 yards, leaving a net residual loss to the shore area of 642,000 cubic 

 yards. Impoundment and shoaling data for Lake Worth Inlet indicates that 

 around 230,000 cubic yards of material moves south annually into the inlet 

 area (Watts, 1962). Even if the entire amount lost at Lake Worth Inlet 

 were bypassed and allowed to reach the littoral zone to the south, a net 

 annual deficit of 412,000 cubic yards of sand would occur in the littoral 

 sand budget south to Government Cut . These figures indicate that such 

 remedial measures as groins and inlet bypassing would not entirely prevent 

 continued erosion of the beaches of southeast Florida and that periodic 

 replenishment of at least some of the loss would appear to be the most 

 effective measure of maintaining suitable beaches in the area. 



3. Areas Suitable for Offshore Borrow 



The density of data collected by CERC for this study is adequate 

 for sand volume calculations in the Miami grid area only. A study of 

 the sand resources on the shelf off Broward County (25°58' N to 26''20' N; 

 Figure 18) was completed in 1967 by Ocean Science and Engineering Company 

 (OSE) for the Broward County Erosion Control Committee who have made the 

 results available to the Coastal Engineering Research Center. The Broward 

 County Study is based on marine seismic reflection profiles run from about 

 100 yards offshore to 1 nautical mile offshore at 600-foot intervals along 

 the entire county frontage; these were supplemented by tivo long cross lines 

 parallel to shore. Sediment characteristics of the bottom and to -12 feet 

 below the bottom were determined by use of several sampling techniques: 

 a 12-foot long airlift sampling device, a water-jet probe, and diver 

 inspection. From the two sources (CERC and OSE studies), it is possible 

 to make reasonably reliable sand volume estimates for most of the region 

 south of 26°20' N (Section A). Only tentative estimates for Section B can 

 be made because of the reconnaissance nature of the CERC Sand Inventory 



35 



