5. Nearshore Circulation and Longshore Transport . 



On the basis of field studies, Harrison and Wagner (1964) proposed 

 that a nontidal drift eddy, with clockwise motion, exists between Cape 

 Henry and Rudee Inlet. 



An investigation of the rate of longshore transport between Cape 

 Henry and the Virginia-North Carolina line by an analysis of wave 

 energy (as computed from Saville's (1954) hindcast data) was made by 

 Weinman (1971) . He determined a net annual transport to the north 

 of 9.8 X 10^ cubic yards per year (7.4 X 10^ cubic meters per year). 

 Although this total is probably too high, the detailed results 

 qualitatively agree with other studies, and emphasize the importance 

 of southeast waves in this area (Goldsmith, et al., 1974b), as dis- 

 cussed earlier. 



Longshore transport rates were also calculated from tracer anal- 

 yses at Rudee Inlet by Bunch (1969). An approximate mean northerly 

 transport of 70,000 cubic yards per year (53,000 cubic meters per 

 year) was calculated from five tests conducted between 8 November 1968 

 and 20 March 1969, during times of moderate wave heights. 



An additional indication of the amount of northerly transport is 

 available from dredging data for Thimble Shoal Channel (U.S. Army 

 Engineer District, Norfolk, 1971). Approximately 1 X 10^ 

 cubic yards (0.76 X 10^ cubic meters) of material is removed every 

 2 to 3 years from just the main channel, located within the Chesapeake 

 Bay entrance (Fig. 1). Tnus, the dredging data probably give only 

 a minimal estimate of the longshore transport along the study area. 



Critical to any research and coastal engineering effort in this 

 area is the location of the nodal transport zone; i.e., the zone 

 where the "net" longshore transport is zero. More specifically, how 

 far south of Rudee Inlet (where sediment accumulates on the south side 

 of the inlet jetties) is the zone where the net southerly transport 

 resumes transport to the south is prevalent on most of the U.S. east 

 coast? 



6. Eolian Processes. 



In relation to long-term viability and preservation of Currituck 

 Spit, the most important processes appear to be eolian. 



There are three basic types of dunes in the study area (except 

 for Profile lines 3 and 4): (a) Vegetated dunes, (b) medanos (i.e., 

 transverse sand hill on the seashore), and (c) parabolic dunes. 



47 



