ABSTRACT
The shoreline along the south shore of eastern Long Island changes regularly in character along an east-west traverse. A profile of the shore zone drawn at any particular point can be used to infer the recent history of that particular segment of shoreline. The coastal profile west of the till cliffs at Montauk indicate a slowly prograding shoreline from Napeague Harbor to East Hampton Village. West of East Hampton the profiles indicate a receding beach with a few segments exhibiting temporary stability. Further west between Shinnecock and Moriches Inlets the form of the shore zone indicates a rapidly receding barrier island.
Data on the migration of the high water line support the geomorphic evidence of shoreline movement. A close correlation of increasing recession rate with the time that Shinnecock and Moriches Inlets were established suggests a causal relationship. Calculations of amount of sand trapped by Shinnecock and the amount removed by increased recession of the shoreline further suggests that the inlets are responsible for accelerated recession on the intervening beaches.
The recession rate of the cliffs at Montauk govern to a large extent the rate of shoreline advance or retreat for beaches west to Shinnecock Inlet. Advance of the shore in the area from Napeague Harbor to East Hampton represents the infilling of a re-entrant along an otherwise straight shoreline. The rate of recession between Shinnecock and Moriches Inlets is explained as the net effect of natural island migration and the result of reduced sand supply. Increase in sea level is not considered to be a significant factor in recession of beaches along the south shore of eastern Long Island.
