influences the refraction path of waves approaching the coast from north to 

 east. The effect of the topographic high is to bend waves approaching from 

 north of shore-normal to approach from the south. This mechanism tends to 

 create a northward-directed current, which supports the inference that an 

 alongshore sediment transport nodal zone exists near latitude 36°4l'. 



105. At Rudee Inlet, the net alongshore transport rate of 2 x 10 cu m/ 

 year based on recent dredging records, is 60 percent of an estimated 

 3.4 x 10 cu m/year cummulative volume loss north of the nodal zone. The 

 latter value is based on long-term shoreline change rates (Figures 28) , the 

 alongshore distribution of those rates, and a 10-m shoreface depth (Haller- 

 meier 1977). Therefore, in recent times 60 percent of the sediments lost from 

 the beaches appear to have moved in an alongshore direction primarily inshore 

 of the ends of the Rudee Inlet jetties (Figure 24). Loss rates in the nodal 

 zone area are based on 130 years' record and variations from one survey to the 

 next were small (Figure 29), indicating that conditions have not varied as 

 much there as elsewhere in the study area. Some of the unaccounted-for 40 per- 

 cent of lost sediment may have been moved west by overwash or wind transport, 

 or east and offshore into water that is deeper than the jetty ends. In addi- 

 tion, the static effect of sea level rise relative to land at 0.4 mm/yr (Hicks 

 1981) on a beach sloping at 1:30 would be a yearly loss of 26,000 cu m, or 

 about 20 percent of the unaccounted-for sediment. Rising sea level may have 

 had an additional, unquantifiable effect on the dynamics of the system. 

 Sound shoreline change 



106. Dune construction, either by natural or artificial means, is 

 usually accomplished at the expense of sand in the littoral zone. To compen- 

 sate for the lost sand, the shoreface and beach profile, and, consequently, 

 the shoreline, will retreat. This was probably the case following construc- 

 tion of the continuous dune between South Nags Head and Cape Hatteras which 

 was begun artificially, using sand fences, between 1936 and 1940. Dune pro- 

 file data and rates at which the dune grew are unavailable; however, if a 

 final 5-m-high-by-60-m-wide dune with about a 3-m-high. overwash platform re- 

 sulted and a shoreface depth (i.e., the depth from mean sea level (MSL) to 

 base of shoreface) of 10 m is assumed, the removal of that volume of sand from 

 the littoral zone would result in a shoreline retreat of 11 m. Dune-building 

 may be a factor in the increased shore erosion between Oregon Inlet and Cape 

 Hatteras between 1917 and 1949 (Figure 45). 



97 



