2. Suitability of Sand for Beach Nourishment . 



Sand should meet certain important criteria to be useful as borrow 

 material for beach restoration and protection projects. Factors to con- 

 sider are the: (a) population mean grain size and total size distribu- 

 tion, (b) mineralogic composition, (c) economics of sand recovery, and 

 (d) placement and distribution on the beach. The borrow material should 

 be of at least the same size and, preferably, slightly coarser than native 

 material on the beach to be nourished. If borrow material was signifi- 

 cantly smaller in particle size than indigenous sand it would be expected 

 to be less stable and out of equilibrium with the wave and current regime. 

 Consequently, it would be rapidly eroded and either carried offshore by 

 wave-induced currents or transported parallel to the beach by longshore 

 currents. In either case the net effect is accelerated retreat of the 

 fill to readjust nearshore profiles, thus requiring considerably larger 

 total volumes of initial fill and more frequent periodic replenishment. 

 If the borrow sand does not have the same grain-size characteristics as 

 the native beach sand, the grain-size population of the borrow sand should 

 preferably be more poorly sorted, i.e., a greater variation in size classes 

 than the native beach sand, and initial overfill relative to the required 

 volume of fill for sand having the same characteristics as that of the 

 native beach would be necessary for comparable performance. 



Borrow material should be composed of hard, chemically and physically 

 resistant minerals, such as quartz, which will not readily degrade in the 

 high-energy nearshore-beach-dune environment. 



The subject of beach fill and its design is covered in detail by 

 Krumbein and James (1965), U.S. Army, Corps of Engineers, Coastal 

 Engineering Research Center (1973), James (1974), and James (1975). 



3. Potential Borrow Areas and Sand Volumes . 



Results if this regional study using vibratory cores and high- 

 resolution seismic records indicate that large volumes of clean sand 

 ubiquitously mantel the Atlantic inner shelf of Long Island from Atlantic 

 Beach east to Montauk Point. Availability of suitable beach fill is less 

 easily documented for eastern Long Island in the Gardiners and Napeaque 

 Bays region; however, data indicate large volumes are present in limited 

 areas. Based on visual examination of the cored sediment and lateral 

 extrapolation of subsurface stratigraphy on the seismic profiles, 14 sea 

 floor areas are judged to contain detritus suitable for restoration and 

 nourishment of area beaches (Figs. 27, 28, and 29). Individual borrow 

 areas are letter-designated and cover the shelf area from the shoreface 



( 30-foot depth; 9.2 meters) seaward to an arbitrary limit of data 



coverage. Normally this seaward limit is the 90-foot (27.4 meters) depth 

 contour; however, in area I off Moriches Inlet the area extends out to 

 the 120-foot (36.6 meters) depth. The cores shown in Figures 27, 28, and 

 29 were closely examined for sand character; the number adjacent to the 

 symbol identifies the core and the parenthetical expression is the minimum 



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