Table 4-3
Estimated Mattituck Inlet Flood Shoal Volumes and Areas,
1935-1938
Volume (cu yd)
Feature
1935
1936
1937
1938
West lobe
outside channel
11,600
19,400
23,400
16,100
West lobe
inside channel
7,100
0
3,100
6,400
West lobe total
18,700
19,400
26,500
22,500
East lobe
outside channel
9,800
5,800
5,700
9,300
East lobe
inside channel
17,600
0
3,400
4,200
East Lobe total
27,400
5,800
9,100
13,500
Flood shoal total
46,100
25,200
35,600
36,000
Area (sq ft)
West lobe
outside channel
102,800
109,200
113,600
86,200
West lobe
inside channel
25,600
0
14,000
17,200
West lobe total
128,400
109,200
127,600
103,400
East lobe
outside channel
90,000
56,300
53,600
80,900
East lobe
inside channel
58,100
0
24,100
28,200
East lobe total
148,100
56,300
77,700
109,100
Flood shoal total
276,500
165,500
205,300
212,500
The original navigation project authorized the jetties to the 9-ft mlw depth
contour (Ralston 1928). The authorized jetty lengths, 1,030 ft for the west jetty
and 775 ft for the east jetty, did not adequately protect the inlet from shoaling.
Sediment intrusion from the west to east, associated with the predominant
direction of longshore transport, augmented by storms from the northwest
quadrant, resulted in rapid shoaling within the channel along the west jetty. In
addition, the shoreline directly east of Mattituck Inlet receded rapidly, causing a
landward breach at the base of the east jetty sometime in the mid-1930s.
Evidence of this landward breach can be seen in Figure 4-17 (circa 1941).
The initial new work dredging of the Federal navigation channel at Mattituck
Inlet was completed in 1914. From June to November 1921, the first
maintenance dredging occurred, removing 13,498 cu yd of sediment. Given the
fact that the next dredging occurred only 2 years later, this dredging is considered
to be an emergency dredging to restore the Federal navigation channel to project
dimensions. Visual inspection of a New York District condition survey dated
30 April 1920 confirms that the channel had greatly shoaled and was nearly non-
navigable.
125
Chapter 4 Morphology Change, and Channel Shoaling and Migration
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