31. Navigation accuracy increased through time. Evidence of this grow- 

 ing sophistication in positioning tools and techniques can be seen in the 

 noticeable decrease in the width of the inlet sequences. Prior to the 19th 

 century, New Currituck, Roanoke, and Chickinacommock Inlet sequences are all 

 at least 5' of latitude wide, while the sequences of Oregon (assuming that 

 the offset of 1861 is a distortion), New, and New/Loggerhead Inlets are all 

 approximately 3' of latitude wide. With time, more accurate measurements re- 

 sulted is less lateral variation in the map position of inlets. Inlet loca- 

 tions on maps other than those produced by NOS are potentially inaccurate by 

 up to ±5 minutes of latitude (i.e., the approximate amount by which early 

 measurement methods could vary and still produce a map with the general con- 

 figuration of the existing shoreline) . This reasoning could help to explain 

 the dramatic change in location of Roanoke Inlet between 1657 and 1770 shown 

 in Figure 9. 



32. Another explanation for the variation over time of inlet locations 

 is north or south inlet migration. The NOS maps show, for example, that 

 Oregon Inlet has migrated south over the past 130 years, at the rate of 29 m/ 

 year, for almost 2 minutes of latitude. If the migration sweep of other 

 inlets falls within the same range, an inlet remaining open for 100 years or 

 so could move ±2 minutes in latitude. 



33. A large shoreline bulge into the sound is often a good geomorphic 

 clue to the presence of an inlet which was open in the past. Currituck Inlet 

 is clearly related to a wide section of the island (Figure 11). Musketo 

 Inlet, however appears to be located several minutes north of a large island 

 bulge (Figure 9); quite likely, the bulge is the site of historic Musketo 

 Inlet. The very large width change from Kitty Hawk to Nags Head is likely re- 

 lated to prehistoric Kitty Hawk Inlet (Figure 12). Roanoke Inlet, shown as 

 having varied widely in an alongshore distance (Figure 9), is centered at a 

 shoreline bulge; possibly more than one inlet existed in this reach. An 

 island bulge is also associated with the sites of the now-closed New and 

 Loggerhead Inlets shown on NOS shoreline maps (Figure 11). 



Continental Shelf 



34. A barrier island shoreline is to a large extent shaped by ocean 

 waves which move across the continental shelf onto the shoreface and break 



26 



