SCALES 



1000 2000 3000 <000 

 METERS 



e.ooo 



FEET 



AMELIA ISLAND 



ir' CUMBERLAND ISLAND 



LEGEND 



I I EROSION 

 I I ACCRETION 



(AFTER OLSON, 1977, 

 FIGURE COURTESY OF OLSON 

 ASSOCIATES, INC.) 



ATLANTIC 



OCEAN 



Figure 4-83. Accretion and erosion over a 100-year period at St. Mary's River 

 entrance, Florida (contours are shown in feet). 



cubic meters (120 x 10 cubic yards) of sand in a giant shoal while the areas 

 adjacent to the shoreline on each side of the jetties (but out of the wave 

 sheltered zone of the jetties) eroded 46 x 10 cubic meters (60 x 10 cubic 

 yards) of sand. Significant shoreline erosion is now occurring in these areas 

 (Olsen 1977). At the time of construction of the jetties shown in Figure 4- 

 82, navigation was a prime consideration and shorelines adjacent to the 

 jetties were not extensively developed. 



5. Littoral Material Trapping at Inlets . 



The potential for inlet systems to tie up sand of the littoral system in 

 their f lood-and-ebb shoals has been documented by Dean and Walton (1973); 

 Walton and Adams (1976); Behrens, Watson and Mason (1977), Watson and Behrens 

 (1976), and others. 



Dean and Walton (1973) have noted that the sand found in the ebb-tidal 

 deltas of inlets is derived from beach sands; the delta sand should be of the 

 same general size distribution as that found on adjacent beaches, in view of 

 the high wave energy expended on the ebb-tidal delta outer bar. Olsen (1980) 

 has found that for Redfish Pass on the lower gulf coast of Florida, the sand 

 and shell sizes in a potential borrow area (for beach nourishment) located on 

 the ebb-tidal delta is somewhat coarser than that found on adjacent beaches. 



4-173 



