to cobble), sediment samples were collected there and analyzed to explore possible
relations among grain size, water movement, and inlet channel cross-sectional stability.
Mattituck Inlet
The 6-8 October 2002 survey of Mattituck Inlet, Mattituck Creek, and the offshore
area adjacent to Mattituck Inlet, was made with an Innerspace 448 high-precision echo
sounder and a Global Positioning System (GPS). Horizontal positional accuracy is
approximately +/-1 m. The Innerspace 448 is a survey-grade depth sounder that employs
a transducer with an 8-deg sounding beam and operates at a frequency of 208 kHz. The
beaches adjacent to the inlet and the area from the shoreline seaward to wading depth
were surveyed with land-based equipment (total station and surveying rod).
At Mattituck Inlet, two Seabird26 Paroscientific Digiquartz Pressure Sensor-based
tide gauges were deployed for the period 19 September - 8 October 2002. Two SonTek
October 2002. Current Meter 1 was placed adjacent to Tide Gauge 2. Grain-size
properties of sediment samples collected 6-7 May 2003 and analyzed by the New York
District are also discussed.
Bathymetry
The extent of the survey for the Mattituck Inlet study area is shown in Figure 3-2,
and interpolated elevation contours for the Mattituck Inlet study area are plotted in Figure
3-3. The survey data were brought into ArcView 3.3 for display and data cleaning.
Areas of shoaling within the inlet, the Federal navigation channel, the channel that runs
through Mattituck Creek, and the Federal anchorage at the end of the creek are observed.
A shoal of unknown origin is located east of the inlet. It is doubtful that this feature is an
ebb shoal. This morphologic feature, longshore bars west of the inlet, the Federal
navigation channel, and the areas of shoaling within the inlet are discussed in the
following sections.
Offshore and east offshore shoal morphology. Figure 3-4 shows the locations of
the offshore survey transects of 6-8 October 2002 west of Mattituck Inlet. Beach profiles
derived from the survey are shown in Figures 3-5a and 3-5b. From the berm crest to a
depth of approximately 10 ft, the beach slope is 1:15. Three longshore sandbars and a
relatively uniform shoreline are observed. The relatively uniform shoreline west of the
inlet is shown in Figure 3-6. Figure 3-7a indicates these longshore bars west of the inlet
and Figure 3-7b indicates the lack of longshore bars east of the inlet. The most landward
or inner longshore bar is located approximately 250 ft offshore, trends toward the
shoreline 2,500 ft west of the inlet, and extends for approximately 7,500 ft west. The
second longshore bar, referred to in this report as the main longshore bar, is located
approximately 750 ft offshore. The main longshore bar begins approximately 2,000 ft
west of Mattituck Inlet, where it trends in towards the shoreline, and continues for at least
28,000 ft. The most seaward bar runs from the tip of the west jetty to 4,300 ft west of the
jetty, where it attaches to the main longshore bar. Adjacent to the east jetty, a bypassing
bar is observed, that connects to the most seaward longshore bar east of the inlet.
Seaward of these bars, the slope is gentler, at approximately 1:125, from 1,400 to 2,500 ft
offshore.
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Chapter 3 Field Data Collection and Analysis
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