Shoreline evolution
There is evidence over the past two years (1998/99) that the north spit is
beginning to migrate back to the south through a series of swash bars and
recurved spit growth. It is unclear in the short term how the spit will react to the
increased dominance of the north ebb shoal. Eventually, the north spit will again
migrate southward prograding Nauset Spit to the south, once again following the
140-year cycle. The last cycle took around 100 years for the spit to grow past the
town's mainland shore.
The South Beach and its land bridge to the mainland will most likely move
southward and landward by overwash and breaching and weld to the mainland
shore as it did in the late 1920s in the last cycle. This process will add large
amounts of sand to the mainland shoreline and eventually the southern part of
Chatham Harbor will disappear. In the distant future the spit will connect Morris
Island with North Monomoy Island. In the meantime, the mainland shoreline may
undergo periods of alternating accretion and erosion as the sand of the shoals and
South Beach migrate in an uneven fashion toward it.
Regional Sand Management
The maintenance of navigation channels at Aunt Lydia's Cove will continue
to be a challenge. It is recommended that in the short-term, dredging of the west
ebb spit of the flood shoal be continued in its general location as shown in Fig-
ure 54. A re-examination of the orientation will be needed after the west flood
channel re-establishes itself and the sand in the detached western part of the flood
shoal takes on its own morphology.
Dredging of the ocean side of the ebb shoal in the vicinity of where the north
ebb channel is located may be necessary in a few years as the ebb shoal and its
two channels evolve. In this transitional period, when two ebb channels are