PART VI: SUMMARY AND CONCLUSIONS 



127. Shoreline change maps of the ocean and sound shorelines from west 

 of Cape Henry to west of Cape Hatteras were produced using historic NOS shore- 

 line maps. The accuracy of the shoreline change maps is estimated to be at 

 least within ±10 m. Using a digitizing procedure, average shoreline change 

 rates were quantified for 2-km-long reaches of the study coast. Predicting 

 the magnitude of shoreline change rates for future years is difficult because 

 of undefined temporal changes in the processes which produce the changes. 

 Relative shoreline change rates, however, can be forecast with some confidence 

 in an alongshore direction; that is, the relative rates at adjacent shore 

 locations can be forecast based on relationships with geomorphic features at 

 or near the locations. The following characteristics of shoreline change in 

 the study area can be concluded from this study: 



a. Shoreline change rates have varied greatly from one time period 

 to another (Tables 11, 12). Because of these variations and 

 the difficulties encountered in attempting to account for them, 

 accurate quantitative forecasts of the absolute magnitude of 

 shoreline change decades into the future are not possible using 

 data acquired in this study. However, very likely the general 

 erosional trend which existed between 1850 to 1980 will 

 continue. 



b. Barrier spits and islands generally narrowed between about 1850 

 and 1980. This narrowing contrasts with geological evidence 

 that the barriers have migrated landward in the past thousands 

 of years. Island migration, in the classic sense, is ocean 

 shore retreat and simultaneous sound shore progradation; i.e., 

 island movement toward the continental landmass. Island nar- 

 rowing in the 130-year study period may be a higher frequency 

 trend within the longer term trend of island migration which 

 occurs in association with sea level rise relative to land. 



c. The barrier islands appear to be too wide (1980) to migrate as 

 the result of overwash processes. Overwash-transported beach 

 sands rarely reach the sound side of the islands. 



d. Island width (Figure 12) correlates well with two inlet systems 

 that existed before 1585 (geomorphic evidence) and inlets that 

 existed after 1585 (evidence in maps and charts). 



e. Inlets in the study area have tended to open and close in 

 specific regions, but not in the same places in these regions. 

 Because inlets often (but not always) caused the island to 

 widen after the inlet closed, the historic inlet area became 

 less susceptible as a site for a new inlet. But because the 

 hydraulic characteristics of the ocean and sound caused the 

 region to remain susceptible as a new inlet site, new inlets 



106 



