Chatham Inlet and Harbor are listed in Table 2. While the inlet quickly formed a
symmetrical ebb shoal with a central east/west oriented ebb channel, the flood
shoal was split into a separate north and south flood shoal, expanding around two
remnant Chatham Harbor shoals. The main ebb channel migrated to the south,
with the ebb shoal forming an asymmetric form to the south as the ebb shoal
expanded. The north swash platform also expanded to the south. The Nauset Spit
end recurved north and west into Chatham Harbor until 1994, when it reversed
direction and moved more to the south and west and enlarged. The South Beach
spit recurved south and west into Chatham Harbor until the south flood shoal and
south remnant sand flat combined with the spit to close off navigational access to
southern Chatham Harbor. The welding of the south spit to the mainland beach in
1992 changed the circulation into north Chatham Harbor and Pleasant Bay. The
remaining north flood shoal migrated and expanded northward. Tern Island and
its associated south shoal evolved as the east and west channels changed course
around the expanding north flood shoal. This expanding flood shoal restricted
navigation into Aunt Lydia's Cove with shoaling of the west channel, requiring
dredging to maintain access to the pier.
Table 2
Key Events in Morphology Evolution
Date
Event
01/02/87
Breach forms during northeaster.
05/87
North and south flood shoals incorporate existing remnant shoals in Chatham
Harbor. Symmetric ebb shoal forms with single ebb channel and north swash
platform.
05/89
South flood shoal overtakes south remnant sand flat.
08/90
Construction completed on mainland shoreline rock revetment.
05/92
South Beach spit attached to mainland beach.
03/94
Nauset Spit ends recurved migration to north, but continues to expand westward
into Chatham Harbor in a series of recurved spits.
05/95
North ebb channel forms through ebb shoal creating a two-ebb channel system.
06/97
South Tern Island shoal removed as navigation channel reorients to a north-
south direction adjacent to mainland shore.
Channel and Inlet Throat Changes
Changes to the throat section between the adjacent beaches and the position of
the ebb channels was quantified by measuring the distance along a common line
drawn along the axis of Nauset Spit between the edge of the north and south spits
off of each yearly photo set. The width of the ebb channels was also measured
where each side of the channel crosses this reference line. A zero point was taken
at the site of the original breach. Figure 20 plots the inlet-throat width and channel
positions, which were updated from Liu et al. (1993). The distance between the
33
Chapter 3 Inlet Throat, Shoreline, and Channel Evolution
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