January 13, 2004
14:37
WSPC/101-CEJ
00097
525
Analytical Model of Incipient Breaching of Coastal Barriers
equilibrium faster for larger initial width, whereas breach depth approaches equilib-
rium faster for small initial width. The volume of the breach approaches equilibrium
faster for larger initial width both because of the large initial width and because
QB > QS in this example.
4. Simulation for 1980 Breach at Moriches Inlet, New York
Moriches Inlet is a federally maintained entrance located on the eastern shore of
Long Island, New York, connecting Moriches Bay (part of the large Great South
Bay) to the Atlantic Ocean (Fig. 11). Without stabilization by structures, inlet
channels on eastern Long Island meander and have maximum depth of about 3 m
with respect to mean lower low water. The ocean mean tide range at Moriches Inlet
is about 1 m. Moriches Inlet has a well-documented history of opening and closing
in the past century (Czerniak, 1977; Schmeltz et al., 1982). The modern inlet was
opened by a storm in 1953 during construction of dual jetties that are spaced 245 m
apart.
After inlet opening in 1953, the barrier island on the eastern (updrift) side of
Moriches Inlet gradually narrowed, primarily due to erosion at the jetty and shoreline
intersection on the back bay. Sorensen and Schmeltz (1982) indicate the adjacent
beach to have been about 100 m wide in 1972 (taken to be L in the simulations
described below). A storm occurring on January 1416, 1980 created a breach at
the narrowest point in the barrier island, about 300 m east of the east jetty. By
May 1980, the breach had enlarged to reach the jetty and grow to approximately
885 m width according to an October observation (see Fig. 12 for a September
Block Island
Sound
Long Island Sound
Montauk
Point
Shinnecock
Manhattan
Bay
Moriches
Bay
Shinnecock
Long Island
Inlet
Moriches
y
h Ba
Sout
Inlet
reat
G
Fire Island
Jones
Inlet
E. Rockaway Inlet
Rockaway Inlet
Scale
Inlet
0
8
16
Kilometers
Atlantic Ocean
Fig. 11. Location map for Moriches Inlet, Long Island, New York.
Fig. 11. Location map for Moriches Inlet, Long Island, New York.
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