It appears that much can be learned about inlet stability through study of the inlets of
the north shore of Long Island because of the substantial difference in coastal
environment as compared to the south shore and to most inlets on sandy coasts in general.
The inlets investigated in this study, Mattituck Inlet and Goldsmith Inlet, are located
5.2 miles apart on the eastern end of the north shore of Long Island, NY. Inlets of
varying size are found along the south and north shores, as well as in the bays of Long
Island. Inlets on the north shore of Long Island have received little study, with the
exception of Stony Brook Harbor (Cooke 1985; Park 1985; Zarillo and Park 1987). The
inlets of Long Island's north shore vary greatly in size and configuration, from large
ones, such as Port Jefferson Harbor and Oyster Bay, to small inlets such as Mattituck
Inlet and Goldsmith Inlet (Figure 1-1). Port Jefferson Harbor and the entrance to Oyster
Bay are of comparable scale to the more extensively studied inlets of the south shore, but
their bay systems are much smaller.
Mattituck Inlet and Goldsmith Inlet are connected to Long Island Sound. Long
Island Sound is a semienclosed tide-dominated water body that communicates with the
Atlantic Ocean at both its eastern and western ends, via Block Island Sound and the East
River (and ultimately, New York Harbor) respectively. The relatively large mean tide
(5.2 ft)1 and spring tide range (6.0 ft) along the Eastern Long Island Sound is one
controlling factor for the stability of both inlets (Figures 1-2 and 1-3).
Mattituck Inlet is a federally maintained channel and connects Long Island Sound to
Mattituck Creek (Figure 1-4). Mattituck Inlet is the only major harbor on the north fork
of Long Island and is a commercial and recreational boating center. Two jetties stabilize
this inlet, and the navigation channel is maintained to a depth of 7 ft mean low water
(mlw) with a 2-ft allowable overdraft. Overdraft refers to the contractually allowable
depth of dredging greater than the authorized depth to account for equipment limitations
and survey accuracy. The inlet was sometimes dredged from the mid 1920s to mid 1970s
for local commercial mineral operations (sand and gravel mining). The tidal prism, the
volume of water entering or exiting an inlet during a flood or ebb tide, is a primary
control on inlet stability and channel cross-sectional area. The present study calculates a
tidal prism of 4.32 107 cu ft at Mattituck Inlet based on measured bay area and half the
spring tide range.
Engineering activities such as surveying and dredging, as well as historic documentation of tide ranges
associated with this study are reported in their original units, U.S. Customary (non-SI) units. As an aid to
those ongoing activities and to maintain continuity with previous publications employing non-SI units, those
units are preserved in the present context. Oceanographic quantities are expressed in SI units. A table for
converting non-SI to SI units is given on page xxiv.
Chapter 1 Introduction