298
Inlet Processes, Massachusetts
DISCUSSION
ACKNOWLEDGEMENTS
As originally reported by BRUUN and GERRITSEN
This study was supported by the U.S. Army Corps of
(1959), the rate of longshore sand transport toward the inlet
Engineers' Coastal Inlets Research Program at the
versus the maximum tidal discharge in the channel govern
Waterways Experiment Station in Vicksburg, MS. We wish
the different mechanisms of inlet sediment bypassing. The
to thank Ted Keon, Director of Coastal Resources, Town of
ratio between these two parameters determines whether
Chatham, MA for assistance in data collection. Special
sand bypasses an inlet primarily by wave action along the
thanks to Nick Kraus, Thad Pratt, and Don Stauble at the
outer bar or through a combination of wave and tidal
Waterways Experiment Station and Ed O'Donnell of the
processes. FITZGERALD (1982) and FITZGERALD et al.
New England District Office for collaboration with this
(2000) presented conceptual models of sediment bypassing
project.
at tidal inlets building on these early ideas. Recently
LITERATURE CITED
GAUDIANO and KANA (2001) have quantified the
volume and rate at which bar complexes bypass inlets along
ALLEN, J.R., LABASH, C.L., and LIST, J.H., 1998. Space
the coast of South Carolina. Sediment bypassing at New
and time scales of shoreline change at Cape Cod National
Inlet is highly dynamic involving both channel switching
Seashore, MA, USA. In: KRAUS, N.C., and
and the formation and landward migration of swash bars.
MCDOUGAL, W.G. (eds.) Proceedings of Coastal
Added complexity stems from the impact changes in the
Sediments '99, pp. 1244 1254.
backbarrier can impose on flow patterns through the ebb
BROOKS, R.M. and BRANDON, W.A., 1995. Hindcast
delta and swash platform. Complex sediment bypassing
wave information for the U.S. Atlantic coast: Update
processes occur at many other inlets and eventually these
1976 1993 with hurricanes, WIS Report 33, U.S. Army
types of processes need to be studied and quantified.
Engineer Waterways Experiment Station, Vicksburg,
MS.
CONCLUSIONS
BRUUN, P. and GERRITSEN, F., 1959. Natural bypassing
of sand at coastal inlets. Journal of the Waterways and
1. Formation of New Inlet was a product of several
Harbors Division, ASCE, 85, 401-412.
processes working synergetically to breach the barrier:
A. Decreasing sediment supply causing long-term
FITZGERALD, D.M., 1982. Sediment bypassing at mixed
energy tidal inlets. Proceedings 18th Coastal
shoreline recession, B. Elevated water levels due to
Engineering Conference, ASCE, pp. 1094-1118.
storm surge and high astronomic tides, C. Segmented
dunes funneling overwash and development of an
FITZGERALD, D. M., 1988. Shoreline erosional-
overwash channel, D. Tidal head which promoted flow
depositional processes associated with tidal inlets. In:
across the barrier.
AUBREY, D.G., and WEISHAR, L. (eds.),
Hydrodynamics and sediment dynamics of tidal inlets.
2. Sediment began bypassing the inlet once the ebb-tidal
Springer, Berlin, pp. 186-225.
delta achieved an equilibrium volume. Most sand
FITZGERALD, D.M., and FITZGERALD, S.A., 1977.
bypassing is accomplished through short breachings of
Factors influencing tidal inlet throat geometry.
the outer main channel through the ebb delta. This
Proceedings of Coastal Sediments '77. ASCE,
process results in the formation of swash bars (100 to
Charleston, SC, pp. 563-581.
300 m in length) that migrate onshore and weld to the
FITZGERALD, D. M., KRAUS, N. C., and HANDS, E. B.,
beach every 1 to 3 years.
2001. Natural mechanisms of sediment bypassing at
3. Although New Inlet is a migrating inlet and contains a
tidal inlets . ERDC/CHL-IV, U.S. Army Engineer
well-developed spit platform, sediment bypassing due to
Research and Development Center, Vicksburg, MS, 12 p.
breaching of the spit platform has not occurred. Short-
FITZGERALD, D.M. and MONTELLO, T.M., 1993.
cut channels have developed across the spit platform but
Backbarrier and inlet sediment response to the
these channels have been unable to capture the bay tidal
breaching of Nauset Spit and formation of New Inlet,
prism over the long-term. Migration of sand shoals and
Cape Cod, MA. In: AUBREY, D.G., and GIESE, G.S.
tidal channels in the backbarrier together with
(eds.), Formation and Evolution of Multiple Tidal Inlet
progradation of Nauset Spit control ebb tidal flow in the
Systems. American Geophysical Institute, Washington,
main channel and ultimately the unstable nature of the
DC, pp. 158-185.
short-cut channels through the spit platform.
Journal of Coastal Research, Special Issue 36, 2002
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