By 27 March 1996, the second northern ebb channel had established in a east-
west orientation some 1,400 ft (427 m) north of the original breach (Figure 16).
The South Beach continued to migrate to the north as the Nauset Spit continued to
migrate back toward the south. The ebb shoal continued to migrate into Chatham
Harbor and expanded its asymmetrical shape to the south, attaching to South
Beach some 5,000 ft (1,524 m) south of the northern tip. With the funneling of
flood flow between the swash platform and mainland point, the flood shoal
expanded in area and its shape was elongated to the north. The west channel was
the access directly to Fish Pier, but shoaling in the channel adjacent to the distal
end of the western ebb spit hampered navigation. With the expansion of the flood
shoal, the east channel was shifted well to east, next to Nauset Spit. The flood
ramp had widened and deepened and was directly adjacent to the main channel
leading to the two ebb channels.
Ten years after the initial opening, the South Beach continued to migrate
westward by overwash processes as the southern main ebb channel remained fixed
against the attached mainland-South Beach shoreline. The 27 June 1997 photo-
graphs showed the increased deposition on the ebb shoal with exposed linear sand
shoals on the central and southern portions during low tide (Figure 17). This
deposition along the ebb shoal made navigation across the southern ebb channel
difficult. The northern ebb channel was becoming more well defined, oriented
almost due east-west, through the ebb shoal and pushing the northern terminal
lobe further seaward. The northern swash platform gained sand, while a new spit
feature formed at the end of Nauset Spit. The flood shoal was becoming more
asymmetric as the flood flow moved the feature northward past Tern Island. A
narrowing west channel separated the island from the flood shoal. Tern Island was
also migrating up the estuary, with erosion on the south end and deposition of
sand flats on the north end. Significant sand flats had also formed in the area to
the north of Tern Island. The south Tern Island shoal, that had defined the
southern side of the Tern Island channel, had completely eroded away by this
time. Navigation into the Fish Pier was direct from the west channel, but shoaling
was still a problem at the southern end of the western ebb spit of the flood shoal.
The main flood flow was over the flood ramp, with extensive shoaling occurring
in the east channel also.
The southward movement of the ebb shoal continued, with extensive over-
wash of the northern end of South Beach. Navigation was difficult at the distal
end of the southern main ebb channel, as of 2 July 1998 (Figure 18). The location
of this channel had become fixed against the shoreline of the attached South
Beach, which hampered further southern migration of the channel. The northern
channel was attempting to establish itself as the main channel, but formation of a
channel margin linear shoal bisected the channel into two channel orientations.
The ebb shoal in general continued to grow into the bay, along with a large
growth in Nauset Spit. The confluence of the landward migrating northern
channel/swash platform/Nauset Spit complex, mainland point and southern
terminus of the flood shoal restricted the tidal flow to create the deep scour hole
detected on the SHOALS bathymetric survey, in the navigation channel. The large
expanse of the flood shoal filled almost the entire bay area. The westward move-
ment of the shoal caused the western ebb shield to again close off access to the
Fish Pier. A channel was dredged by the Town of Chatham through this spit to
28
Chapter 3 Inlet Throat, Shoreline, and Channel Evolution
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