American Society of Civil Engineers

Discriminating Modes of Shoreline Response to Offshore-Detached Structures

by Ian L. Turner, (Sr. Res. Fellow, Water Res. Lab., School of Civ. and Envir. Engrg., Univ. of New South Wales, King St., Manly Vale, Sydney, NSW 2093, Australia. E-mail:

Journal of Waterway, Port, Coastal and Ocean Engineering, Vol. 132, No. 3, May/June 2006, pp. 180-191, (doi:

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Document type: Journal Paper
Abstract: Offshore-detached structures are used to limit shoreline erosion, and to provide a safe haven for marine craft or bathers. Their function is to reduce the amount of wave energy in their lee, and to enhance sediment deposition at the shoreline. Planform shoreline changes in the vicinity of an offshore structure represent the integrated effect of natural shoreline variability, and engineering factors including sand nourishment, the formation of a shoreline salient, and a secondary “groyne effect” induced by a gradient in the alongshore transport. To quantitatively assess a structure’s performance, it is necessary to first distinguish the structure-induced effects from the pre-existing shoreline variability, and second to discriminate and quantify these differing modes of shoreline response. The easily applied technique “odd—even function analysis” can be used to discriminate the principal modes of shoreline behavior in the vicinity of offshore-detached structures, and to distinguish this induced response from naturally occurring shoreline variability. The successful application of the technique is illustrated to identify early trends in coastline adjustment in the lee of a new submerged reef structure at the Gold Coast, Australia.

ASCE Subject Headings:
Shoreline changes
Offshore structures
Beach erosion