4
Ebb and Flood Shoal
Evolution
A second task was to categorize ebb and flood shoal development and evolu-
tion patterns. Identification of change in area and an estimate of volume in the six
identified shoals/adjacent shores from the previous study (Weishar, Stauble, and
Gingerich 1989) has been updated to the new configurations of today. Six areas of
inter- and subtidal shoals and the two spits were identified based on typical inlet
morphology (Hayes 1980; Boothroyd 1985). As the new inlet developed, the basic
inlet shoal morphologies formed. The eight shoals and adjacent spits of the inlet in
1989 were as follows:
a. Oceanside.
(1) Ebb tidal delta - was the most prominent feature on the ocean side of
the inlet. It formed as a symmetrical feature with one main ebb
channel and progressively became more asymmetric in shape as the
prevailing coastal processes caused the shoal and main ebb channel
to migrate southward.
(2) Swash platform - was a large sand body that developed on the north
side of the southward migrating main ebb channel and expanded
with multiple swash bars.
(3) North spit - the spit at the distal end of Nauset Beach began to
migrate north and west into Chatham Harbor as the inlet throat
expanded.
(4) South spit - the spit at the northern end of the South Beach barrier
island migrated landward and south into Chatham Harbor as the inlet
throat expanded.
b. Bayside.
(1) South remnant shoal/flood tidal delta - this preinlet sand shoal was
incorporated into the southern part of the flood shoal as the inlet
opened.
(2) North remnant shoal/flood tidal delta - a preinlet sand shoal that
evolved into the north flood shoal as the inlet established.
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Chapter 4 Ebb and Flood Shoal Evolution
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