of a convergent nodal zone. (Watson, 1971.) Nodal zones o£ divergence 

 are more common than nodal zones of convergence, because longshore trans- 

 port commonly 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 direc- 

 tions, but because of insufficient data, the location of the mid-point of 

 the nodal zone may be uncertain by up to 10' s of miles. 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 inter- 

 pret 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 Fig- 

 ure 4-57, 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 Shinne- 

 cock Inlet, which is navigable. 



( 14 September 19691 



Figure 4-57. South Shore of Long Island, N.Y., Showing Closed, 

 Partially Closed, and Open Inlets 



4-146 



