the predominant south-directed longshore transport does not return it to the inlet (Elwany et al.
2003). The opening of the lagoon reduces flooding to property and improves water quality in the
estuary.
Coastal ponds on the Atlantic coast.
Coastal ponds on the Atlantic coast are often
mechanically breached for environmental reasons and to reduce the risk of flooding. On the
south shore of Long Island, NY, Mecox, Sagaponack, Wainscott, Georgica, and Hook are all
brackish ponds that are breached, typically annually or more frequently, to alleviate flooding and
improve water quality. The ponds are breached by digging a pilot channel with conventional
earth-moving equipment from the ocean toward the pond and from the pond toward the ocean,
leaving a sand plug in a convenient location to be excavated. The plug is removed at low tide
and preferably during a period of low waves to prevent premature closure of the breach by
longshore transport. Figure 10 shows a recent breach cut made at Sagaponak Pond. The
breaches are left unattended to close naturally by infilling through longshore transport. As a
breach closes, the ephemeral ebb shoal created by the opening may weld to shore and contribute
to closure and beach healing (Kraus et al. 2002). Smith and Zarrillo (1988) document the
natural closure of Mecox Pond after mechanical opening.
Figure 10. Breach cut at Sagaponak Pond on Long Island (looking toward pond),
4 March 2005.
Typically, pond opening is conducted during time of low tide and moderate to calm wave
conditions. In this way, water will ebb from the pond rapidly, increasing the width of the breach,
while minimizing formation of a flood shoal. An increase in volume of the flood shoal decreases
pond area and removes sediment from the beach.
CONCLUSIONS: The case studies reviewed in this technical note document lessons learned
through experiences with mechanical breaching and closure of breaches. Experience has taught
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