d. The feature is located too far to the east to be associated with the inlet as
an ebb-tidal shoal.
The origin of the offshore shoal is unknown. It may be a pre-existing geologic
feature, and a portion of it may be the result of dredged material placement
during the new work dredging of Mattituck Inlet.
Goldsmith Inlet, Conclusions
The presence of a tidal mill at Goldsmith Inlet in the eighteenth and
nineteenth centuries indicates stability of the channel and strong tidal flow prior
to the partial modifications of 1963-1964 as part of proposed and later abandoned
marina development. The construction of a jetty on the west side of the entrance
and the new-work dredging (1964) promoted stability of the inlet by interrupting
longshore transport of sediment to the east for approximately 14 years. In 1978,
the jetty at Goldsmith Inlet appears to have reached impoundment capacity.
After impoundment capacity was reached, rates of sediment intrusion into
Goldsmith Inlet increased. An increased sediment supply resulted in dynamic
morphological evolution within Goldsmith Inlet, partially mitigated by dredging,
initially by Suffolk County and later by the Town of Southold. The increased
rates of sediment intrusion resulted in the creation of an attachment fillet or spit
directly east of the inlet, the eventual maturation of the flood shoal, and a
subsequent increase in the rate of channel infilling.
The reestablishment of an effective natural longshore sediment bypassing
system appears to have taken place sometime in the early 1980s, when the
attached fillet east of the jetty reached an areal extent that promotes bypassing.
Partial dredging from 1980 to 2000 apparently mitigated the continued growth
and maturation of this attached fillet, and the eastward migration of the inlet
entrance. The lack of dredging in recent years (in addition to the continued
degradation of the jetty) has allowed for rapid growth of this feature, and
resulting eastward migration of the inlet entrance (2001-2002). Reestablishment
of a natural system of sediment bypassing has occurred, where sediment is
transferred from this attached fillet via a bypassing bar located near the swash
zone and eventually to the beach east of Goldsmith Inlet.
The current through Goldsmith Inlet is strongly flood dominant, controlled in
main part by the shallow sills in the channel. Because sediment transport is
proportional to a power of water velocity, such as the third power, net sediment
transport is directed into Goldsmith Pond. The greater velocity magnitude at the
inlet mouth entrains and transports larger grain sizes. Because the current
velocity magnitude decreases with distance into the inlet, gradational deposition
occurs, with the larger grain size fractions deposited and finer sediments
transported further into the inlet.
Tidal asymmetry of coastal inlets has been well studied (e.g., Boon 1975;
Boon and Byrne 1981; Aubrey and Speer 1985; Speer and Aubrey 1985; Speer
et al. 1991), as recently summarized by Walton (2002). For example, shoaling
channels truncate the lowest portion of the tide, resulting in a longer falling tide
and a weaker ebb current as compared to the flood current. Such a truncation is a
hypsometric effect, the control of water-surface elevation by the bathymetry or
depths. In the case of Goldsmith Inlet, the elevation of the entire inlet entrance is
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Chapter 7 Comparative Analysis and Conclusions
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