6 Inlet Morphology and
Stability
The morphology of an inlet is a consequence of a dynamic balance among
the factors of hydrodynamic forcing, geologic setting, supply and transport of
sediment in and near the inlet, and any artificial manipulations such as jetty
construction and dredging. Classification methods describing the large-scale
features of inlets (ebb shoal, flood shoal and inlet channel) are available (e.g.,
Bruun and Gerritsen 1959, 1960; Hayes 1980). Empirical relations have been
derived that relate the tidal prism of an inlet to its channel cross-sectional area
(e.g., LeConte 1905; O'Brien 1931, 1966; Jarrett 1976; Byrne et al. 1980), and a
method for estimating inlet channel cross-sectional area stability is also available
(Escoffier 1940). Jarrett (1976) and Byrne et al. (1980) examined the width-to-
depth ratio W/D of inlet channels to characterize the hydraulic efficiency.
Relations have been also been derived to predict the volume of inlet ebb shoals
(Walton and Adams 1976) and flood shoals Carr de Betts (1999) based on tidal
prism.
In this chapter, the channel and shoal morphologies of Mattituck Inlet and
Goldsmith Inlet are examined through available qualitative and quantitative
approaches, incorporating data and calculation results presented in preceding
chapters.
General Inlet Properties
Studies that explore the quantitative properties of morphologic features of
inlets are reviewed in this section as preparation for application to Mattituck Inlet
and Goldsmith Inlet.
Inlet classification and sedimentation patterns
Hayes (1977) and Davis and Hayes (1984) introduced a classification
procedure that places inlet morphology within a continuum ranging from tide
dominated to wave dominated (Figure 6-1). At tide-dominated inlets, ebb shoals
tend to be large (relative to the flood shoal) and intertidal at their crests.
Sediment (sand) bypassing occurs through the mechanism of "tidal bypassing,"
(Bruun and Gerritsen 1959, 1960) by which sediment is initially brought into the
inlet from the updrift side by the flood tide and then transported to the downdrift
side by the ebb current. Mattituck Inlet and Goldsmith Inlet fall into the category
of tide-dominate inlets according to Figure 6-1. However, there is a large gravel
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Chapter 6 Inlet Morphology and Stability
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