3
Inlet Throat, Shoreline,
and Channel Evolution
Chatham Harbor Evolution
Preinlet
Since the mid 1800s breach, the South Beach had migrated westward and
merged with the mainland and Monomoy Island. Nauset Spit began its trek
southward and the inlet migrated south ahead of the spit. During the early 1980s
Nauset Spit was in the southward growth part of the morphologic cycle, with
Chatham Bars Inlet located seaward of North Monomoy Island, around 1 mile
(1.6 km) south of Morris Island Cut. Figure 5 shows the configuration of Chatham
Harbor in its preinlet state on 20 October 1982. Nauset Spit is continuous across
the Town of Chatham shorefront. A north and south remnant shoal are present
along with a south remnant sand flat in Chatham Harbor. The center line of the
main channel through the harbor meanders around these shoals, but is for the most
part in the center of the elongate lagoon. The entrance channel to the Fish Pier and
Aunt Lydia's Cove is located between the southern end of Tern Island and a
shoal, and is orientated in a east-southeast direction. The mainland beach is wide
and has a spit oriented to the south, coming off of the shore and attaching to the
south remnant shoal.
The approximate location of the 2 January 1987 breach is in a narrow section
of Nauset Spit, just across the harbor to the north of the Chatham Lighthouse.
This area had few dunes and was bisected by several low spots created by foot
traffic and off-road vehicles. The lack of dunes and low elevation allowed the
storm surge to cut through to the bay and establish the inlet.
Morphologic evolution of inlet 1987 - 1999
The first vertical aerial photography was flown five months after the breach,
on 7 May 1987. Figure 6 shows the early stages of inlet development with the
formation of an ebb shoal on the ocean side. At this time, the ebb shoal had a
symmetrical crescent shape. A swash platform was beginning to form in the inlet
throat just off the northern spit. A south flood shoal formed in the bay and encom-
passed the southern remnant shoal. Sand was also growing on the north flood
shoal that had attached to the north remnant bay shoal. The main ebb channel
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Chapter 3 Inlet Throat, Shoreline, and Channel Evolution
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