THE U.S. ARMY CORPS OF ENGINEERS' COASTAL INLETS RESEARCH PROGRAM

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Barry W. Holliday 1, E. Clark McNair2, M. ASCE, and Nicholas C. Kraus3, M.ASCE

ABSTRACT: Federal agencies are being required to do more with less. The U.S.

Army Corps of Engineers must maintain existing federal inlet and entrance channels

and respond to authorizations for channel deepening and new channels with a budget

that does not increase commensurately. The answer to serving the Nation's needs in an

era of declining resources is to advance understanding of inlet processes and

incorporate this knowledge in operation and maintenance practices of navigation

projects. The Coastal Inlets Research Program was established 5 years ago with the

mission of advancing knowledge and developing predictive technology to reduce the

cost of dredging, promote navigation channel reliability, and understand the sediment-

sharing interactions between inlets and adjacent beaches. This paper describes this

productive research program and introduces selected results.

INTRODUCTION

Navigation projects located at coastal inlets are designed, operated, and maintained through

complex morphologic features. These features evolve with time scales and rates ranging from

short as in the response to storms to the gradual change exceeding a century as caused by

normally occurring waves and currents (Fig. 1). Because the hydrodynamics, inlet morphology,

navigation channel, and longshore sediment transport are connected, consequences of navigation

project maintenance and natural processes must be estimated to minimize channel dredging and

to promote sediment bypassing, either by natural processes or through dredging-related

activities. In addition to gradual long-term trends, near-discontinuous and periodic changes can

occur as a result of storms, changing weather patterns, dredging, and modifications to jetties.

Both conceptual and quantitative models of stabilized inlets that operate at geomorphic time

scales are lacking, and engineering practice at inlets is based on limited tools available for

evaluating project alternatives. Quantitative predictive models must be developed that can

calculate navigation channel and morphology change, such as at ebb shoals and flood shoals, and

connect the processes to the channels and adjacent beaches. Predictive capability is expected to

occur based on recognition of the space and time scales associated with the target process, as

shown in Fig. 1, and discussion below is put in context of the scales in this figure. Improved

predictive capability will aid in estimating the performance of channels to be deepened,

evaluating advance maintenance dredging, controlling channel migration, reducing channel

shoaling, and preserving and promoting sediment pathways to adjacent beaches.

1) Dredging and Navigation Branch, Construction and Operations Division, Headquarters U.S. Army

Corps of Engineers, 441 G Street, NW, Washington, DC 20314.

2) Clark McNair Consulting, 303 Pinehurst Street, Vicksburg, MS 39180. ClarkMc@canufly.net.

3) U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, 3909

Halls Ferry Road, Vicksburg, MS 39180; .