shortening of the Goldsmith Inlet jetty to half its length and installation of groins at
selected locations downdrift of the inlet. Although the stability of Goldsmith Inlet was
not explicitly addressed, its possible closure and the resulting environmental and water
quality problems were considered in the recommendations.
Contemporaneously with the present study, in support of the New York District,
Batten and Kraus (2005) performed a Section 111 analysis for the downdrift (east) shore
at Mattituck Inlet. Section 111 of the River and Harbor Act of 1968 authorizes studies
for the prevention or mitigation of shore damages attributable to Federal navigation
works. Batten and Kraus (2005) analyzed shoreline change both updrift and downdrift of
Mattituck Inlet in a regional context, including development of a sediment budget for the
coastal area adjacent to the inlet.
Motivation
Inlet properties of bay size, tide range, wave height, sediment size, and location on a
wave-sheltered or unsheltered coast have been found to influence the stability relation
between inlet tidal prism and cross-sectional area. These and other processes, such as
potential geologic controls and wave steepness, can be investigated at Mattituck Inlet and
Goldsmith Inlet. The apparent longevity and locational stability of Mattituck Inlet and
Goldsmith Inlet, as compared to much larger inlets on the south shore of Long Island
warrants attention. Why should such relatively small inlets be so stable?
Small inlets offer a convenient opportunity to investigate inlet morphodynamics
because of their limited size and greater accessibility. Byrne et al. (1980) found that the
relationship between changes in inlet cross-sectional area and flow regime differed for
small inlets. Through the analysis of width-to-depth ratios found at both small and large
inlets, they concluded that small inlets must be more hydraulically efficient than large
inlets to maintain stability. Goldsmith Inlet is similar in size to those studied by Byrne et
al. (1980), whereas Mattituck Inlet is larger, but yet small as compared to the 108 inlets
analyzed by Jarrett (1976) in developing predictive relationships for inlet channel cross-
sectional area.
The close proximity of these inlets, one a federally maintained inlet (Mattituck Inlet),
and the other a seminatural inlet (Goldsmith Inlet), provides an opportunity to examine
the dynamics and stability of small inlets in an engineered condition and an almost
natural condition, respectively. Although they share the same wave climate and the same
tidal forcing, the differences in tidal prism and number of jetties benefit a comparative
study of inlet stability. Mattituck Inlet is dredged for navigation, is stabilized by two
jetties, and has a channel composed predominantly of sand and gravel-sized sediment.
Goldsmith Inlet is dredged infrequently, is shallow and non-navigable, has one jetty that
is fully impounded, and is substantially armored by gravel (Figure 1-7).
NY, Appendix II-A1, unpublished report.
9
Chapter 1 Introduction
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