This study of Mattituck Inlet and Goldsmith Inlet, Long Island, NY, covers the historic and geomorphic background, literature, field measurements, numerical modeling of tidal circulation, and analysis of inlet morphologic properties. The inlets are located 8.2 km apart on the eastern end of the north shore of Long Island, NY, facing Long Island Sound Mattituck Inlet has a federally maintained channel and dual jetties, and it connects the sound to Mattituck Creek. Mattituck Inlet is the only major harbor on the north fork of Long Island is a commercial and recreational boating center. The navigation channel is maintained to a depth of 7 ft mean low water with a 2-ft allowable overdraft. Goldsmith Inlet connects the sound to Goldsmith Pond. The inlet has a nonfunctional jetty on its west side and is non-navigable, with typical depths ranging from 0.5 to 3 ft.
Tidal inlets on the north shore of Long Island have received little study compared to those on the south shore that open to the Atlantic Ocean. It appears that most inlets on the north shore have been more stable and in existence longer than the inlets on the south shore. Inlets on the north shore, therefore, hold value for further understanding of basic inlet processes, in particular, of channel cross section and locational stability. Another motivation for the study of inlets along the north shore of Long Island is the large range in grain size of the sediments on this coast.
Given their significant differences, it is remarkable that Mattituck Inlet and Goldsmith Inlet have remained open for more than two centuries and likely much longer. The stability of inlets on the north shore derives in part from a relatively steep inner shore face, presence of geologic controls such as shard points on shore, origins of ponds as low-lying areas created after glaciation, and relatively weak longshore sediment transport that is about an order of magnitude less than that on the south shore of Long Island. However, other factors enter in controlling stability, in particular, commercial mining of sediment, such as at Mattituck Inlet.