Headland Sand Bypassing: Byron Bay

Peter Cowell (University of Sydney Institute of Marine Science)

Photos by Mexican (David Sumpter): taken at The Pass, Byron Bay, to monitor sand pulsing.


November 2003
May 2004

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Beaches, banks and coastal processes

Sand bypasses Cape Byron (SE Australia) from south to north as littoral drift driven by waves from the south east and their associated surfzone currents. The drift rate is estimated at 250,000 cubic metres per year but fluctuates by an estimated average of plus or minus 70,000 cubic metres per year (Gordon, Lord and Nolan, 1978).

The fluctuations occur as sand pulses, with good banks and good surf at the Pass at Byron Bay during the passage of a sand pulse. Between pulses the banks and the beach disappear and the surf is hopeless. Beach erosion also sets in at Byron Bay (especially Belongil). The erosion is probably worst immediately preceding arrival of the next sand pulse.

 The sand pulsing may be related to short term climate fluctuations (e.g., the El Nino Southern Oscillation) which causes alternation between periods dominated by storms and fairweather, and variations in the average direction of waves (tending more from the south or more from the north during successive periods). Variation in average wave direction causes a rotation of the shoreline (Cowell and Thom, 1994; Short, Cowell, Cadee, Hall, and van Dijk, 1996). If beaches south of the Cape (i.e., updrift in the sand transport pathway) experience clockwise shoreline rotation, then sand spills around Cape Byron at a faster rate causing a sand pulse.

  

Cowell, P.J. and Thom, B.G., 1994. Coastal impacts of climate change - modeling procedures for use in local government. Proceedings 1st National Coastal Management Conference, Coast to Coast'94. Hobart, June. 43-50.

Gordon, A.D., Lord, D.B., and Nolan, M.W., 1978. Byron Bay - Hastings Point Erosion Study. Report No. PWD 78026

Short, A.D., Cowell, P.J, Cadee, M. Hall, W. and van Dijk, B. 1996: Beach rotation and possible relation to the Southern Oscillation. Proceedings Int. Conf. Ocean and Atmosphere Pacific, Adelaide, October 1995, 329-334.

Short, A.D, Trembanis, A.C, and Turner, L.T, 2001. Beach oscillation, rotation and the Southern Oscillation, Narrabeen Beach, Australia. Proceedings International Conference on Coastal Engineering, Sydney 2000, American Society Civil Engineers, 2439-2452.