GRAVITY DRAINAGE: A NEW METHOD OF BEACH STABILISATION THROUGH DRAINAGE OF THE WATERTABLE

Greg A. Davis, David J. Hanslow, Kevin Hibbert, Peter Nielsen

Abstract


Beach nourishment to provide an erosion buffer and increase amenity is a well established coastal management option and is favoured because it is a relatively "soft" option with few aesthetic drawbacks. This paper describes how enhancement and stabilisation of the natural accretion processes may be achieved by a low-cost beach drainage system. The project described here shows that the watertable and shoreline can be lowered by a drainage system installed in the beachface. A prototype system was installed on Dee Why Beach, New South Wales, Australia in February-March 1991 and has been continuously discharging water until the present (November 1992). A number of minor storms have exposed and caused some damage to drainage material but the system continues to work. Survey data are being collected at regular intervals to show the effects of the drainage system on the watertable and the morphology of the beach. Analysis of changes in morphology in both drained and undrained segments of the beach shows a significantly more stable beachface in the area of the drained beachface.

Keywords


gravity drainage; beach stabalization; beach drainage; watertable

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