the frequency and intensity of storms, but the general pattern will follow the
prevailing coastal processes, which are unchanged from past cycles.
Dredging practices to date have centered around the navigation to the Fish
Pier and have been limited to the Aunt Lydia's Cove area. A comparison of the
average annual shoal dynamics (based on a measure of area change and estimated
volume) to quantities of dredging showed that the amount of sand removed was
on the order of less than 1 percent of the overall inlet sand volume. Most of that
material was placed on Tern Island or on the mainland beaches that have experi-
enced erosion due to the inlet evolution. Future dredged material disposal should
be kept in the system and be placed in anticipation of erosion problems based on
the general Chatham Inlet cycle. In-water disposal of material on the shallow
seaward edge of the ebb shoal is possible and will allow sand to remain in the
littoral system and bypass to the south. The main trend will be for South Beach to
migrate south and west and finally weld onto the mainland opposite Morris Island.
(This phase of the cycle took around 50 years on the last cycle.) For some time the
mainland shoreline will be open to the ocean as the breakup and landward move-
ment of South Beach occurs. Nauset Spit will over time migrate south and bypass
the mainland shoreline again being lead by the southward migration of the throat
of Chatham Inlet (a process that took 100 years on the last cycle).
The dredging currently authorized by regulatory approval, to maintain a
navigable entrance channel to the anchorage in Aunt Lydia's Cove consists of
removing less than 10 percent of the volume of the current north flood shoal in
any given year and in practice has removed on the order of 1 percent of the
volume of the existing flood shoal during the last several dredging operations. The
location of the dredging area on the west ebb spit of the north flood shoal is some-
what removed from the main inlet geomorphology and sediment dynamics and
should have negligible impacts on the evolution of the inlet. The main processes
that affect the dredging area are ebb and flood tidal flow on the western edge of
the flood shoal. A new re-establishment of the west flood channel by natural
forces will have a significant effect on modifying the tidal circulation and mor-
phodynamics of this north flood shoal area that has been expanding up-estuary
and growing laterally since inlet formation.
The largest dynamics occur on the ebb shoal/swash platform area and this area
is presently undergoing a large natural perturbation in the switch of the dominant
ebb channel from the former south ebb channel to the recently formed north ebb
channel. The North Beach spit has also undergone a shift from a general pattern of
growth to the west into the bay with the development of several recurved spits, to
a more southerly migration of the entire spit form over the past 2 years, as was
common immediately after formation. This change to a dominant north ebb chan-
nel over the ebb shoal and a smaller north swash platform will play a more signifi-
cant role in the migration and evolution of the north spit over the next few years
than any dredging of small quantities on the western edge of the flood shoal.
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Chapter 7 Conclusions
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