needed on the land bridge to slow any possible catastrophic breakup of South
Beach, although at present, the area is a nesting ground for Piping Plover.
At the present time, the quantities being dredged from the entrance channel
and anchorage at Aunt Lydia's Cove to maintain navigation to the Fish Pier are
small relative to the inlet as a whole. The volume of material removed has been
less than 1 percent of the entire inlet sand volume and appears not to have affected
the evolutionary pattern of the inlet shoals or adjacent shorelines. Placement of
76 percent of the dredged material has been within the inlet system with 26.7 per-
cent being placed on eroding mainland beaches near the inlet opening to stabilize
landward retreat of the shoreline. The location of dredging on the west side of the
flood shoal is off to the side of the main tidal circulation within Chatham Harbor.
Continued dredging in the locations currently proposed for the newest dredging
operation and any additional near future dredging are only enhancing the natural
channel patterns to keep open navigation to the Fish Pier.
Current regulatory approvals allow for up to 100,000 cu yd (76,460 m3) to be
dredged within the area of the entrance to Aunt Lydia's Cove within any single
year, with a cap of 350,000 cu yd (267,610 m3) in a 5-year period. To date,
dredging volumes have been well below this annual volume, except in 1994/95.
The present volume of the north flood shoal is estimated to be near 1.1 million
cu yd (0.84 million m3), so the maximum allowable dredging volume per year is
about nine percent of the total shoal volume. If this maximum amount of sand
were to be removed in any year, there still would be minimal impact on the
growth of the north flood shoal.
The impact of this dredging in the vicinity of Aunt Lydia's Cove on the
growth of the north flood shoal appears to be minimal. The small amount of sand
removed to maintain the navigation channel opening through the west spit of the
flood shoal is not changing the natural northward migration patterns of the flood
shoal or the growth and redevelopment of the natural west channel in its preinlet
orientation. Natural processes are much more dominant in the evolution of the
inlet. Sand moves southward in the direction of dominant drift along the ocean
side of Nauset Spit. The southward and westward growth of the spit resumed in
1998 after several years of westward movement of the spit into the bay (1990-
1993) and northeastward recurving (1994-1997). The present natural change from
the dominance of the south channel through the ebb shoal to the newly developed
north channel will further affect this migration rate of the spit and growth of the
swash platform. The north channel will probably develop into the dominant
channel and proceed to migrate southward. As this happens, Nauset Spit and the
north swash platform will most likely resume a more southward growth. From
past cycles, the southward movement of the inlet could take several years (up to
50 years based on the last cycle) to move Nauset Spit past the present inlet posi-
tion. The South Beach will probably break up through overwash events that will
migrate the barrier island and the present ebb shoal westward until it welds onto
the mainland. This south and westward migration of the South Beach and present
ebb shoal will allow Nauset Spit and the inlet to migrate south also.
85
Chapter 6 Dredging Plan Recommendations
Previous Page
