Pond, facing the Atlantic Ocean on the south shore of Long Island, New York. Without almost
annual artificial breaching, water level rises in the pond, and basements of bordering residences
flood. The artificial breaching, or "pond letting" as referred to by the residents, has been
conducted at Mecox Pond for more than a century. The breach is left unattended to close under
littoral processes, as documented by Smith and Zarillo (1988). Several California river entrances
such as the Carmel River, Russian River, and Salinas River are artificially breached for such
purposes as prevention of flooding of farmland and to open migration paths for salmon.
Unintended breaching of barrier islands and spits can be a serious concern in developed areas
or where critical habitat is endangered. A breach can cause loss of human life, flooding and
wave attack, loss of property or access to property, loss of habitat, exposure of the bay or
estuarine environment to ocean waves, and unwanted changes in salinity and water level.
Figure 2 shows Little Pikes Inlet, the name of the breach that opened from the seaward side on
eastern Long Island, New York (Terchunian and Merkert 1995), in December 1992. The barrier
island breach gradually increased in width from about 30 to 1,500 m, forming a semi-permanent
inlet that was later closed at considerable expense. Besides loss of structures in the path of the
breach, its presence denied access to homes and the county park located on the western side.
Tide range and salinity in the back bay increased while the breach was open. Breaching of the
barrier island or spit near a jetty, such as reported by Sorensen and Schmeltz (1982) for Moriches
Inlet, New York, can compromise the structure by stranding it. For these reasons, the New York
District of the U.S. Army Corps of Engineers, in cooperation with the State of New York, has
developed a breach-contingency plan for the south shore of Long Island that includes strategic
stockpiles of sand and rapid communication lines between Federal and State Governments to
close breaches quickly that may open during storms.
Breaching can lead to formation of a new inlet that may compete favorably for dominance of
the tidal prism and stability with existing inlets in the same bay system, possibly promoting their
closure. A trend toward closure of an existing inlet, particularly if stabilized by jetties, can make
navigation unreliable and may hold environmental consequences because of changes in water
level and circulation pattern. Breaching of barrier islands, spits, and river mouths occurs
throughout the United States every year. Despite its potential significance, barrier breaching has
received little study as compared to other coastal geomorphic processes. Basco and Shin (1999)
developed a one-dimensional (1D) model of overwash and incipient breaching (their model did
not scour a deep gorge) by combining 1D storm surge and wave models with the SBEACH
model of beach profile change (Larson and Kraus 1989; Larson et al. 1990). The work of Basco
and Shin is pioneering and reveals many questions to be answered. Visser (1998) summarized
engineering analysis performed in The Netherlands to understand and model breaching of dikes.
The northern coastal stretch of Humboldt County, located in northern California, is
characterized by a succession of headlands defining pocket beaches and lagoons backed by
mountain slopes and meadows. The Humboldt Lagoons State Park is comprised of four lagoons
that are isolated from the Pacific Ocean by wide and high barrier sand spits extending between
adjacent headlands (see cover photograph of this issue of Shore & Beach). From south to north
they are Big Lagoon, Dry Lagoon (drained in the early 1900's to serve as farmland), Stone
Lagoon, and Freshwater Lagoon (Figure 3). The region is bounded on the south by a large
headland, Patricks Point, and on the north by Redwood Creek, part of the Redwood National
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