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
present, currents may not be strong enough to maintain a clear channel through
the terminal lobe of the ebb shoal. Eventually, one of the channels will become
more dominant and the ebb flow will be able to maintain an open passageway to
the ocean. Dredging was not necessary in this area when the inlet first opened
since the single main ebb channel was sufficient to maintain a channel as it
migrated to the south. The removal of small quantities of material to facilitate safe
passage over the ebb shoal as the inlet evolves to a more dominant north channel
may be necessary. There should be little adverse impacts if the dredged material is
bypassed to the south, mimicking the natural processes.
A regional sand management plan needs to take into account the long-term
cycle that has occurred at Chatham at least twice in its recorded history. Short-
term remedial action should be based on the general trends that will most surely
occur in this third cycle. Disposal of the dredged material should be in anticipa-
tion of future changes and needs. This cycle has started out slightly different from
the past cycle in that only one inlet is now draining the Chatham Harbor and
Pleasant Bay estuary system. The present inlet has formed at the site of the
southern inlet of a two-inlet system of the past cycle. Each cycle will be driven by
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Chapter 7 Conclusions
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