A notable result for consideration of sediment transport is that the calculated
current velocity at the inlet entrance has a maximum of only about 0.5 m/sec for
the spring tidal conditions simulated. The maximum current through the entrance
would be less for typical tide and neap tide. It is empirically known that the
annual mean-maximum velocity to maintain a minimum stable inlet channel
cross section is about 1 m/sec for inlets on sandy coasts. Because the coarser
sands and gravel predominant at Mattituck Inlet would require even stronger
current velocity than 1 m/sec to sweep the channel clear, it can be concluded that
the channel cross-sectional area is greater than the minimum (for sandy coasts).
Figures 5-9a and 5-9c display near-maximum flood- and ebb-tide current
velocities within the channel. Figures 5-9b and 5-9d show these current velocity
vectors overlaying the inlet and Federal navigation channel bathymetry. The
greatest velocities occur adjacent to the area of the flood shoal along the east
bank, opposite the area of shoaling, where Mattituck Inlet takes a sharp turn to
the east and the channel becomes constricted. Magnitude of velocity reaches
0.5 m/sec.
Figure 5-9a.
Near-maximum flood-tide velocity, Mattituck Inlet, 1200 GMT,
7 October 2002
218
Chapter 5 Circulation Analysis
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