ebb shoal swash platforms. The reduced area and extended length has caused this
channel to narrow and shoal-in, therefore carrying less of the tidal prism of the
inlet. While there are two channels, the flow has not been strong enough to estab-
lish a definite outlet and shoaling and shifting channels are common. This has
presented difficult navigation conditions over the terminal lobe at the seaward end
of both channels. Shoaling and poor navigation will continue, as the north channel
becomes the dominant channel. This may take some time, given the size and
complexity of the ebb shoal and its three swash platforms.
South Beach land bridge
As of 1992, the South Beach spit grew west and incorporated the south flood
shoal and south remnant shoal as it welded to the mainland beach in front of the
present Chatham Lighthouse. This event greatly changed the circulation pattern of
the four inlet multiple system and made the new Chatham Inlet the single opening
for north Chatham Harbor and Pleasant Bay. Since that time the northern tip of
South Beach has undergone severe erosion and migrated landward. This sediment
bridge is subject to beach scarping and overwash during high-water level events.
As of now, the shoreline extending between South Beach and the mainland is in a
relatively stable position. If the past inlet cycles are any indication of the future,
South Beach will continue to lose sediment and migrate landward. In the most
extreme case, the island will break apart with several breaching episodes in the
future as the general island mass moves toward the mainland.
Mainland shore evolution
Since the opening of Chatham Inlet, the shoreline on the mainland directly in
front of the inlet has undergone erosion and shoreline retreat. A rock revetment
composed of a series of individual private and some public structures was com-
pleted by 1990 to protect the upland infrastructure along the shoreline most
threatened. As the inlet evolved, an erosion wave moved both to the south and
north of this severe erosion area. Further south and north, sand was accreting as
spits along the beachfront. The welding of South Beach to the mainland in 1992
reversed the erosion trend to the beach in front of Chatham Lighthouse and to the
South Beach area. What had been a retreating shoreline became an accretionary
shoreline, with the accretion migrating north as the land bridge gained sand over
time.
In the later years, erosion has occurred on the mainland beaches adjacent to
the rock revetment. On the north end of the revetment, dredged material was
placed on the beach at the foot of Claflin Landing . Adjacent to the south end of
the revetment, sand was placed on the beach at Andrew Hardings Lane, in
between this revetment and a smaller rock revetment to the south. This sand
placement has slowed the shoreline retreat trend in this erosion-stressed area. At
the present time the mainland beaches adjacent to the rock revetment are main-
taining their position.
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Chapter 7 Conclusions
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