3 Field Data Collection and
Analysis
As part of this study, a bathymetric survey was performed, and measurements were
made of the water level and current at Mattituck Inlet and Goldsmith Inlet from mid-
September to mid-October 2003. Measurement procedures and results are presented in
this chapter. Previous sediment analysis studies at Mattituck Inlet and Goldsmith Inlet
are also discussed.
Overview of Measurements and Vertical Datums
Shoreline position east and west of these inlets have been surveyed previously (OCTI
1998; Fields et al. 1999), and the New York District surveys the Federal navigation
channel at Mattituck Inlet regularly. Prior to the present study, synoptic bathymetry data
were lacking for the channels and offshore at Mattituck Inlet and Goldsmith Inlet. At
Goldsmith Inlet, prior to the present work, no bathymetric survey of Goldsmith Pond was
available, and at Mattituck Inlet offshore surveys covering the offshore shoal were
available from 1927 and 1967 (the 1927 survey was recovered from archives as part of
this study). Comprehensive surveys allow analysis of morphology change at the inlet
channels and their shoals.
The bathymetric surveys were conducted during 6-8 October 2002. Survey data
presented here are referenced to the horizontal datum New York State Plane Grid, Long
Island Lambert, North American Datum 1983 (NAD83), in feet. Elevations are
referenced to the North American Vertical Datum 1988 (NAVD88) in feet. Horizontal
and vertical controls for the land-based survey were obtained from a March 1998
shoreline survey performed by OCTI (1998). For the period of record of the water-level
gauges deployed in this study, the tidal datum mean sea level was found to be within
survey error of NAVD88 offshore of Mattituck Inlet, at the tip of the west jetty, and
0.25 ft higher than the NAVD88 datum in Mattituck Creek. At Goldsmith Pond, msl
datum for the period of record was found to be 0.91 ft higher than NAVD88. Datum
trees that illustrate the relations between the various datums referenced in this study are
provided in Figures 3-1a and 3-1b.
Water level and current measurements were scheduled for spring tide. The data
collection occurred in autumn, when water level in Long Island Sound tends to be
slightly higher than the annual or long-term average (Lyles et al. 1988). Because of the
wide range in sediment grain size at Goldsmith Inlet (from sand
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Chapter 3 Field Data Collection and Analysis