migrated at least 3.2 kilometers inland from about 5,000 years B.P., 

 given a steady sea level rise. Most sea level curves show a significant 

 slowing in sea level advance at about 4,000 to 5,000 years ago (e.g., 

 Curray, 1965; Milliman and Emery, 1968; Kraft, 1971), so the assumption 

 can be made that recession rates were much greater before about 4,000 

 years B.P. 



The concept of a continuously retrograding barrier island complex 

 requires some consideration of the resulting sediment budget. Barrier 

 island retreat results in erosion of both the shoreface and the beach 

 (Swift, et al., 1972). Sandy sediments exhumed from the shoreface become 

 a part of the retrograding coastal sands, which are either recycled in 

 the barrier complex or lost to offshore deposition. Sediments recycled 

 in the barrier island complex are not lost to the system, but simply 

 deposited as washover fans, inlet fill, dunes, prograding spits, and 

 local aggradation along the beach. The significance of these various 

 considerations is that a large percentage of sediments eroded from a 

 receding barrier island is required for maintenance of the barrier; the 

 only external source of sediment is shoreface erosion, part of which 

 aggrades on the sea floor (Bruun, 1962) and part of which may be trans- 

 ported onto the beach, as suggested by Pierce (1969) and Pilkey and 

 Field (1972). 



b. Depositional Patterns of the Barrier Island Complex . At the 

 north and south end of the study area are large spits which have been 

 steadily accreting since earliest historical surveys. Cape Henlopen is 

 growing north and west into Delaware Bay (Fig. 35, C). Kraft and Caulk 

 (1972) plotted past and present positions of the spit; the estimated 

 rate of growth of the spit is on the order of 10 meters per year. At 

 the southern end of Assateague Island littoral sediments are rapidly 

 building the recurved Fishing Hook spit (Fig. 35, D). Results of succes- 

 sive surveys of the spit tip between 1902 and 1933 are shown in Figure 

 36. The tip of the spit migrated nearly 1,829 meters during the 25-year 

 period, 1908 to 1933, for an average rate of about 73 meters per year. 

 The barrier island coast of northern Delmarva, from Bethany Beach to 

 Fishing Hook, is approximately 72 kilometers (40 nautical miles) long. 

 Assuming a constant growth at the above rate, an adequate supply of 

 sediment, and minimal interference from other budget variables, the 

 whole of Fenwick Island, Ocean City, and Assateague Island conceivably 

 could have been constructed by simple longshore transport in less than 

 1,000 years. This simplistic approach is unrealistic for many reasons, 

 but it serves to point out the potentially significant role that long- 

 shore sediment movement might play in the evolution of the coast. 



The process of retrogradation of the coast is accomplished primarily 

 by the transfer of sediment from the front of the barrier to the middle 

 and back side. Main mechanisms of transfer are by dune formation, inlet 

 filling, trapping of windblown materials, filling of inlets by longshore 

 transport, and washing of beach sands over the island to the back side. 

 (See Fig. 18 for location of historical inlet sites along Ocean City and 

 Assateague Islands.) Many other such inlets were probably formed and 



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