diverges at exposed shores and converges toward major gaps in the ocean shore, 

 such as the openings of New York Harbor, Delaware Bay, and Chesapeake Bay. 



Nodal zones are usually defined by long-term average transport directions, 

 but because of insufficient data, the location of the midpoint of the nodal 

 zone may be uncertain by up to 10' s of kilometers. In addition, the short- 

 term nodal zone most probably shifts along the coast with changes in wave 

 climate. 



The existence, location, and planform of inlets can be used to interpret 

 the littoral processes of the region. Inlets occur where tidal flow is 

 sufficient to maintain the openings against longshore transport which acts to 

 close them (e.g., Bruun and Gerritsen, 1959). The size of the inlet opening 

 depends on the tidal prism available to maintain it (O'Brien, 1969). The 

 dependence of inlet size on tidal prism is illustrated by Figure 4-56, which 

 shows three bodies of water bordering the beach on the south shore of Long 

 Island, New York. The smallest of these (Sagaponack Pond) is sealed off by 

 longshore transport; the middle one (Mecox Bay) is partly open; and the 

 largest (Shinnecock Bay) is connected to the sea by Shinnecock Inlet, which is 

 navigable. 



( 14 September 1969) 



Figure 4-56. South shore of Long Island, New York, showing closed, 

 partially closed, and open inlets. 



Detailed study of inlets through barrier islands on the U.S. Atlantic and 

 gulf coasts shows that the shape of the shoreline at an inlet can be 

 classified in one of four characteristic planforms (See Fig. 4-57, adapted 

 from Galvin, 1971). Inlets with overlapping offset (Fig. 4-58) occur only 



4-140 



