Coupled Circulation, Wave, and Morphology-Change Modeling, Shinnecock Inlet, New York

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Frank S. Buonaiuto, and 2Adele Militello

Abstract

Analysis of five high-resolution bathymetric data sets collected at Shinnecock

Inlet, NY indicates the evolution of ebb shoal morphology between 1994 and 2000

was primarily controlled by migration of the main navigation channel. Increased

wave activity during the 1997 El Nino accelerated the rate at which the channel was

deflected toward the west. These bathymetric data are applied in this study for

assessment of morphology change calculation conducted within the Inlet Modeling

System developed by the U.S. Army Corps of Engineers Coastal Inlets Research

Program. Circulation, sediment transport, and morphology change were calculated

by the two-dimensional finite-difference model M2D, which was coupled with

STWave for computation of wave-driven currents. A simulation was conducted for

August to November 1997 in which waves from NDBC Station 44025 were input as

forcing for STWave. Tidal forcing for M2D was prescribed with water levels

extracted from a regional ADCIRC model. Major observed changes in inlet

morphology were reproduced by the modeling system. These changes are: scour and

westward migration of the navigation channel, accretion along the eastern flank of the

ebb shoal, and accretion of the seaward extent of the ebb shoal.

Introduction

Shinnecock Inlet, located on the south shore of Long Island, New York (Fig. 1),

opened on September 21, 1938 during the passage of the Great New England

Hurricane (Morang 1999). Since its opening, inlet evolution has been influenced by

storms, dredging, beach nourishment projects, and construction and rehabilitation of

two offset rubble-mound jetties originally built between 1953 and 1954. Morphology

of the inlet and ebb shoal is controlled by tide and wave-driven transport, as well as

by jetties and bathymetric features such as channels and shoals. Tide on the south

shore of Long Island is semidiurnal with a mean range of 0.88 m at the inlet entrance

(ocean side). Spring tide range is 1.1 m and the tidal prism is 3.29 x 107 m3 (Militello

and Kraus 2001). Incident waves have average height of approximately 1 m and

1) Coastal Oceanographer. Marine Sciences Research Center, SUNY at Stony Brook, Stony

Brook NY 11794-5000. fsbuonaiuto@optonline.net.

2) Physical Oceanographer. Coastal Analysis LLC, 4886 Herron Road, Eureka, CA 95503.

CoastalAnalysis@cox.net.