formed around 1740 (Giese 1988). Monomoy Island (originally part of the spit)
moved west and became attached to Morris Island and the mainland. Nauset Spit
migrated to the south again, with its tip approximately at the present new Chatham
Inlet (Figure 2). Nauset Spit continued its migration to the south until 1846, when
a new inlet broke through the spit approximately 2 miles (3.2 km) north of the
1987 inlet breach. Much of the shoals in the eastern side of Pleasant Bay are rem-
nant ebb and flood shoals of this inlet. In November 1871, a second inlet breached
the southern barrier in almost the same place as the present breach, just opposite
the Chatham Lighthouse, which had twin light towers at that time (Weishar,
Stauble, and Gingerich 1989). The barrier island was breached in numerous
places through the 1880s and left the mainland basically unprotected from the
ocean waves. Chatham's shoreline suffered severe erosion including the loss of
the two lighthouses. Remnants of the southern barrier island at times welded onto
the mainland and at other times acted as barrier islands as the entire system
migrated west.
Some 50 years after the first breach (between 1910 and 1916) the southern
barrier was welded to the mainland. From a 1929 topographic map, a continuous
barrier spit connected the mainland to Morris Island and Monomoy Island. Nauset
Spit was in the processes of migrating south again, but the shoreline between the
present Fish Pier and Pleasant Bay was open to the Atlantic through a roughly
2-mile- (3.2-km-) wide inlet. In the late 1950s Morris Island Cut was formed
during a winter storm separating Monomoy Island from the mainland once again.
Nauset Spit continued to migrate south and moved past Morris Island Cut, form-
ing the Chatham Bars Inlet. The ebb tidal delta formed at the distal end of Nauset
Spit with a large swash platform in front of Monomoy Island (Hine 1975). Morris
Island Cut became the flood tidal delta of the Chatham Bars Inlet until it migrated
south past the cut. Around 1978, a storm bisected the westward retreating
Monomoy Island in the present location of the unnamed inlet forming the North
and South Monomoy Islands. This unnamed inlet opened just to the south of the
southerly migrating Chatham Bars Inlet/Nauset Spit ebb delta/swash platform
complex. This cycle of westward migration of Monomoy Island and southward
migration of Nauset Spit continued with the breach of 1987.
Coastal processes
The predominate wave approach direction along Nauset Spit is from the east-
northeast (Liu et al. 1993). A mean Hmo of 4.92 ft (1.5 m) with a mean Tp of 8 sec,
based on the Wave Information Study (WIS) update is presented for sta 91
(Brooks and Brandon 1995). This wave station is approximately 7 miles (11 km)
offshore in 299 ft (91 m) of water, so these wave statistics are considered deep-
water open-ocean conditions, which have not been transformed to shallow coastal
statistics. There is a seasonal trend with the largest waves occurring in the winter
months. A resulting southward longshore sediment transport rate has been esti-
mated to be between 4.7 105 cu yd/year (3.6 105 m3/year) (Weishar, Stauble,
and Gingerich 1989) and 6.5 105 cu yd/year (5 105 m3/year) (Liu et al. 1993).
The outer coast at Chatham has a mean tidal range of 6.7 ft (2.0 m) at Chatham
(National Oceanic and Atmospheric Administration (NOAA) 2000). The tide
range has changed significantly in the estuary since the opening of the breach.
4
Chapter 1 Introduction