Channel elevations and hwl location for 4 May 1936, immediately after the
dredging of November 1935 to May 1936, are shown in Figure 4-19a. The areal
extent of the flood shoal is illustrated in Figure 4-19b. The shoreline of 4 May
1936 is illustrated in Figure 4-19a, referenced against the shoreline of
8 December 1927, and the landward breach near the base of the east jetty is
clearly apparent. It is inferred that sediment was transported to the east bank by
landward bypassing during times of high tide and storms. It is appropriate to
consider this feature a spit onto which the east lobe of the flood shoal attaches
itself. Because this spit is dredged only if it encroaches upon the Federal
navigation channel, a portion was not removed. This portion remains in the
system and has evolved into what is considered as the modern-day flood shoal.
The dredging of November 1935 to May 1936 restored the Federal navigation
channel to project depth. Figure 4-19c plots the net change in elevation as a
result of the maintenance dredging of November 1935 to May 1936. In some
areas, the elevation change is extreme. Near the base of the jetties, the channel
has a tendency to migrate to the west, and dredging served to reposition the
navigation channel back to project specifications. Dredging reduced elevation by
16 ft in the area where the flood shoal was removed. An increase of 12 ft
occurred where landward bypassing deposited sediment along the inside of the
base of the east jetty. An increase of 8 ft occurred near the west bank of the
channel, presumably a result of repositioning the channel.
Figure 4-19a. Mattituck Inlet channel elevation, 4 May 1936
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Chapter 4 Morphology Change, and Channel Shoaling and Migration
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