anchorage. After the inlet opened, the north flood shoal began to trap sand as the
tidal flow made the sharp bend to the north into north Chatham Harbor. The shoal
expanded to the northeast as well as toward the east. The entrance channel moved
to the north through 1990 above the expanding and northward migrating shoal
(Figure 58). The west channel was deflected to the west around the widening
flood shoal from 1990 to 1994 (Figure 59). As the west flood channel was moving
west, the entrance channel changed from an east-west orientation in 1990 to a
more north-south orientation beginning in 1991. As of 1994, the west flood chan-
nel was up against the mainland shore, north of Claflin Landing and the Tern
Island south flood shoal was also deflating. This channel reorientation contributed
to eroding the shoreline and bottom scour of the Tern Island south flood shoal's
shallow tidal flat. With this change in orientation, the entrance channel became
shorter in length through the west ebb spit.
As the north flood shoal expanded, the west flood channel was truncated by
the expanding ebb shield and a flood ramp developed that occupied the southern
portion of the channel position by 1995. The west ebb spit of the flood shoal
expanded west, moving closer to the mainland shore. The growth in sand on the
ebb shield area of the flood shoal actually bisected the west flood channel and the
shoaling severely limited navigation to the northern Chatham Harbor and Pleasant
Bay. The entrance channel (now in a north-south orientation and functioning as a
marginal ebb channel) became a bypass around the shoal to gain access to both
the anchorage and the north bay area. As the flood shoal encroached up the
estuary, the ebb shield and west ebb spit all but closed off the west flood channel
(Figure 60). In 1998 and 1999 dredging of this west ebb spit off Claflin Landing
was required to maintain what had become the only viable path. The progression
was for a more north-south entrance channel to be forced over against the main-
land shore by the expanding flood shoal.
The anchorage area within Aunt Lydia's Cove began to have shoaling prob-
lems, particularly along the eastern Tern Island side, as the north flood shoal
evolved. Tidal current velocities have increased in this area as the entrance chan-
nel orientation has moved to a more north-south orientation. Tidal flow that
originally was in the west flood channel was now diverted somewhat into the
anchorage area, around the growing ebb shield. Ebb-dominated shoal patterns
developed to the north of the anchorage as the tidal flow was diverted through the
anchorage by the growth of large sand flats north of Tern Island.
West flood channel
As of 1995 the west flood channel was for the most part closed off by the
westward and northward growing flood shoal. What had been the predominant
channel up to Pleasant Bay had been forced out of position by the flood shoal
growth and eventually became shoaled in. Beginning in 1996, small spillover
lobes had formed in the ebb shield as ebb currents from the upper bay tried to
flow out to the inlet, but was restricted since no distinct channel was present.
Beginning in 1997 and becoming more well established by 1999, a very large
spillover lobe had formed in the historical position of the preinlet west flood
channel and appears to be attempting to break through the flood shoal and
87
Chapter 7 Conclusions
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