south along the North Carolina coast past 

 Cape Hatteras (Gray and Cerame-Vivas 1963; 

 Stefansson et al . 1971). Inshore currents 

 south of Cape Hatteras are variable. 

 South-flowing geostrophic currents are 

 periodically interrupted by inshore 

 movement of the Florida Current, which 

 forces a northward flow (Bumpus 1973). 

 However, the general direction of 

 longshore drift is from north to south. 



2.5 TIDES AND WAVES 



The mean tidal range is less than 1.5 

 m along the coast of North Carolina, 

 increases in South Carolina, and reaches a 

 maximum of 2 m in Georgia (Figure 4). 



South of Georgia the tidal range decreases 

 again, and is only 1 m at Cape Canaveral, 

 FL. In the classification of Davies 

 (1964), the South Atlantic Bight is micro- 

 tidal (tidal range <2 m) along the North 

 Carolina coast, meso-tidal (tidal range >2 

 and <4 m) in southern South Carolina and 

 Georgia and micro-tidal once again in 

 central Florida. 



Wave height varies inversely with 

 tidal range (Nummedal et al . 1977). Mean 

 annual wave heights range from 1.7 m at 

 Cape Lookout, NC, to 0.8 m at 

 Jacksonville, FL. The inverse relation 

 of tidal range and wave height produces 

 barrier islands and tidal inlets of 

 different types. This is discussed in 

 Chapter 5. 



a* 

 •<o 1 



I 



"5 







a 

 o 

 O 



o 



Figure 4. Mean tide level and mean tidal range in the 

 South Atlantic Bight (U.S. Department of Commerce 

 1987). 



2.6 SEDIMENTS 



Most sand found on the beaches in the 

 South Atlantic Bight comes from the 

 adjacent Continental Shelf (Neal et al . 

 1984). It is pushed up to the beach by 

 fair-weather waves. Sand is carried 

 laterally by longshore currents that move 

 in the surf zone parallel to the beach. In 

 general, this movement is from north to 

 south in the South Atlantic Bight, although 

 this can be reversed by a variety of local 

 factors. Massive relocation of sediments 

 can occur during hurricanes and winter 

 storms, called northeasters. This 

 relocation depends on the interaction of 

 longshore currents, tides, and waves and is 

 discussed in Chapter 5. In the 

 Southeastern United States, most sediment 

 carried to the coast by rivers is deposited 

 near the heads of estuaries (Neal et al . 

 1984). However, some of this sediment is 

 eventually resuspended by wave and tidal 

 action and is moved out through inlets into 

 the longshore sediment transport system. 



