b. The temporal trend, but not the magnitude, of east-facing ocean 

 coast changes was similar north and south of Oregon Inlet 

 (Figure 45). 



c. North- and south-facing ocean coasts (Figure 46) were accre- 

 tional in the 5- to 10-km study reaches west of the capes for 

 all survey periods. The trends of change were not similar; 

 however, the small number of reaches sampled in each area 

 (Table 11) may preclude a realistic comparison. 



d. The west-facing shoreline trend in the sounds was one of con- 

 tinuous change from progradation (movement into the sounds) 

 to retreat (movement toward the ocean) between 1852 and 1980 

 (Figure 45). The trends were similar north and south of Oregon 

 Inlet. 



e. Between 1852 and 1980, the north-facing shoreline west of Cape 

 Hatteras decreased its net retreat (Figure 46). This trend was 

 the opposite of that measured for the west-facing sound shore- 

 line (Figure 45) . 



f . Ocean and sound shoreline changes generally did not follow 

 similar trends through time. While the east-facing ocean 

 shoreline retreated at a maximum rate between 1917 and 1949, 

 the west-facing sound shoreline (i.e., the shoreline on the 

 other side of the barrier island) reached a maximum retreat 

 rate in the 1949-1980 period. Only the north-facing ocean 

 shoreline at Cape Henry and the north-facing sound shoreline 

 at Cape Hatteras (Figure 46) showed similar behavioral trends 

 through time. 



Changes in island width and position 



91. Where data covering both ocean and sound shorelines are available, 

 an analysis of island width and position provides useful information on the 

 particular ways in which the islands have changed shape. When averaged for 

 the period of about 1850 to 1980, the east-facing ocean shore retreated an 

 average 0.8 m/year. In the same period the average retreat rate of the west- 

 facing sound shoreline was 0.1 m/year. This resulted in an average island 

 narrowing of 0.9 m/year. 



92. Because the average ocean shore retreat exceeded the average rate 

 of sound shore retreat, the island axis (i.e., the midpoint between shore- 

 lines) moved landward (west) an average 0.35 m/year. However, as Table 13 

 shows, in most time periods and along most reaches, the island axis moved sea- 

 ward at more locations than it moved landward. This island axis movement, 

 though, should not be confused with the classical definition of barrier island 

 migration which assumes that both oceanside and soundside shorelines move 

 toward the continental land mass. Island migration occurs when the ocean 

 shoreline erodes and, concurrently, the sound shoreline progrades as sand is 



84 



