The channel condition surveys discussed in this section are referenced to the
mlw datum employed by the surveyors. As discussed in the previous section, the
New York District mlw datum for this time period is believed to be 3.63 ft below
NAVD88.
The dredging history of Mattituck Inlet (Table 2-5) can be consulted to
estimate the rate of sediment accumulation in the navigation channel. Dredging
is usually performed on an as-need basis (every 10 to 15 years), and sometimes
advance dredging is undertaken. These physical and economic constraints
confound interpretation of dredging records and obscure efforts to make a one-to-
one comparison between volume of sediment shoaled and volume of sediment
dredged (Kraus and Rosati 1998). Dredging at Mattituck Inlet has also been
conducted over varying spatial extents. If records are available over a
sufficiently long interval, however, as is the case for Mattituck Inlet,
uncertainties are reduced.
Natural morphology and initial modifications (1891-1914). The Rivers
and Harbors Act of 19 September 1890 authorized a preliminary examination and
survey of Mattituck Inlet that resulted in a favorable recommendation for inlet
modification. The inlet was considered to have modest economic potential and
was seen as a good harbor of refuge. Mattituck Creek in its natural state was
winding and approximately 2-4 ft deep. Figure 4-10 shows the Mattituck Inlet
hwl shoreline of 1891, referenced against the original configuration of the
Federal navigation channel jetty, the present configuration of the Federal
navigation channel, and the original jetty lengths of 1914. Kraus and Rosati
(1997) discuss definitions of the shoreline, including the hwl.
The orientation of Mattituck Inlet in its natural state resembled that of
Goldsmith Inlet prior to the recent dredging of 22-26 March 2004 (Figure 4-106),
where a narrow spit directed to the east, the dominant direction of sediment
transport, developed. Another example of similar morphology on the north shore
of Long Island is found at Stony Brook Harbor, where a large, well-developed
east-directed spit exists (Cooke 1985; Park 1985; Zarillo and Park 1987).
Figure 4-11 shows the hwl shorelines of Mattituck Inlet for the year 1900.
The morphology of Mattituck Inlet has changed significantly, and a west-directed
spit is observed. This west-directed spit is believed to have evolved into what is
now the eastern lobe of the flood shoal. The reversal in the inlet entrance
orientation observed here is consistent with temporary closure and subsequent
reopening of the inlet.
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Chapter 4 Morphology Change, and Channel Shoaling and Migration
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