6
Mattituck Jetty and
Mattituck Jetty
Mattituck Creek
Mattituck Creek Water Level
4
2
0
-2
-4
10/5
10/7
10/8
10/6
5- 7 October 2002 GMT
Figure 3-23b. Mattituck Inlet water level, 4-8 October 2002
The phase lag, τ, between the two water-level gauge locations was calculated by
determining the time difference between the respective peaks and troughs of each tidal
cycle. The modal phase lag for the measurement duration was 6 min, with the median
value of 5.1 min. As expected, the peaks and troughs at Tide Gauge 1 typically led those
of Tide Gauge 2. Because there was a time interval indicating a phase reversal, only
those cycles when the offshore led the back bay were selected to calculate the median
phase lag. From approximately 1400 GMT on 6 October 2002 to 1500 GMT on
7 October 2002, a phase reversal was recorded, when the peaks and troughs inside
Mattituck Creek led those offshore by 12 to 18 min. A change in phase was not observed
at Goldsmith Inlet for this time period. The reason for the reversal is not known.
The median phase lag allows an estimation of the equivalent cross-channel depth of
Mattituck Creek between the two tide gauges. The celerity C of a long wave is
along-channel and cross-channel depth between the two gauges. With the length λ =
5,200 ft between water-level gauges, the equivalent depth is h* = λ 2 / gτ2 = 9 ft, for τ =
5.1 min (median lag). This value is consistent with the average water depth in the
dredged channel at msl.
67
Chapter 3 Field Data Collection and Analysis
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