wave crests for the most part approaching parallel to shore. Wave gage 

 data and observers supported the view that the longshore current generated 

 off Wrightsville Beach or nearby vicinity must have been relatively weak. 



The sediment plume off Carolina Beach Inlet is much larger in areal 

 extent than the plume off Masonboro Inlet. This phenomenon can be 

 explained by the tidal hydraulics of the area. A detailed analysis of 

 the tidal flow through Carolina Beach Inlet was during a study investi- 

 gating erosion at Carolina Beach (U.S. Army Engineer District, Wilmington, 

 1970} . This analys.is revealed that tidal flow through the inlet is 

 controlled not only by the ocean tide fluctuations but by the fluctuations 

 of the Cape Fear River through Snow's Cut. High water in the ocean occurs 

 about 1 hour before high water in the river; low water occurs about 1.5 

 hours before low water in the river. The result of this combined tidal 

 action is that slack water before ebbtide at the inlet occurs 1 hour after 

 low water in the ocean and slack water before floodtide occurs 1.5 hours 

 after ocean high water. On 4 December 1972, slack water times (e.s.t.) 

 for the ocean, Carolina Beach Inlet, and the Cape Fear River were as 

 follows : 



Ocean River Inlet 



(hours) (hours) (hours) 



0829 (high water) 0929 0959 (slack water before floodtide) 

 1551 (low water) 1721 1651 (slack water before ebbtide) 



Based on this information, at the time of the ERTS-1 image shown in Figure 

 3 (1021 hours e.s.t.), Carolina Beach Inlet was at the beginning of the 

 floodtide cycle and not ebbtide as indicated by Table 4 which gives tidal 

 data from Masonboro Inlet. Therefore, what is observed in the ERTS-1 

 photo is the plume at Carolina Beach Inlet that resulted from the preceding 

 ebbtide cycle; what is seen at Masonboro Inlet is a partially developed 

 plume about 2 hours after the beginning of the ebbtide cycle. 



2. Density Mass . 



A definable color (or gray tone) change in the ocean water off the 

 North Carolina coast is visible in the four bands of the ERTS-1 imagery 

 recorded on 2 June 1973 (ERTS 1314-15210, Fig. 4). The water adjacent to 

 the coast is a lighter color (darker in the negative print) and appears 

 to be a linear mass, irregular in outline and running roughly parallel to 

 shore. The mass extends from the southern frame border north to Rich 

 Inlet, fades out, and picks up again at Old Topsail Inlet. Approximate 

 width of the mass is 7 miles from shore seaward. Examination of the 

 adjacent frame to the south (ERTS 1314-15213, not shown) reveals that the 

 mass is bordered on the south by the shoals off Cape Fear (discussed 

 later). The mass does not contain visible patterns suggesting a tidal 

 outflow. Its irregular outline suggests that mixing with adjacent ocean 

 water is in progress. The visibility of the mass in all four MSS bands 

 indicates the feature has some depth. 



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