Keywords
transect line
predominant waves
erosion hazard
swash zone
dune toe
sediment
swash
berm
How to Cite
Abstract
The coast of New South Wales (NSW), Australia is about 2000 km long and consists of 721 sandy beaches (68%), rock coastline (32%), and more than 185 estuaries. It is most populated in Australia and one of the NSW greatest assets with significant economic, social and environmental values. The NSW coast has epsodically been ravaged by severe storms together with large ocean waves and high water levels, resulting in severe dune-beach erosion/recession, damaging coastal infrastructure and properties and degrading coastal ecosystems. With potential changes to storm-wave climate and rising sea level, coastal erosion hazards on the NSW coast are likely to worsen in the future. This study was undertaken to collect essential field data on beach-dune profiles and sediment grain-size distributions over more than 200 sandy beaches to assess NSW coastal erosion hazard. For each of the selected beaches, three beach-dune profiles of shore-normal transects at 50m apart were surveyed by RTK-GPS, and three sediment samples only on the first transect line were also colleced from the dune, dry beach/berm and swash zone by using a simple hand grabbing method. A sediment grain size analyzer, Malvern Mastersizer 2000E, was used to obtain sediment grain size distributions. It is found that the 618 sediment samples analysed consist of fine sand (10%), medium sand (82%) and coarse sand (8%), and that the dune sand d50 correlates well with the dry-beach sand d50 and is about 8% smaller, but less well correlates with the swash sand d50 and is about 15% smaller. The beach orientation was estimated from the direction of the shore-normal transect lines and generally ranges from 90o to 150o. The beaches surveyed are found to have erosion problems when they were directly exposed to predominant waves in the south-east direction and also when the dune toe elevations were lower than 3~3.5m (AHD). A conceptual model is also developed to assess likelihood storm erosion of a beach-dune system.References
Blott, S.J. and Pye, K. (2006). Particle size distribution analysis of sand-sized particles by laser diffraction: an experimental investigation of instrument sensitivity and the effects of particle shape. Sedimentology, Vol. 53, pp. 671-685.
Cheetham, M.D., Keene, A.F., Bush, R.T., Sullivan, L.A. and Erskine, W.D. (2008). A comparison of grain-size analysis methods for sand-dominated fluvial sediments. Sedimentology, Vol. 55, No. 6, pp. 1905-1913.
Di Stefano, C., Ferro, V. and Mirabile, S. (2010). Comparison between grain-size analyses using laser diffraction and sedimentation methods. Biosystems Engineering, Vol. 106, No. 2, pp. 205-215.
Folk, R. L., (1968). Petrology of Sedimentary Rocks. Austin, University of Texas Publication, 170 pages.
Hanslow, D, Nielsen, P and Hibbert, K (1996). Wave setup at river entrances. International Conference on Coastal Engineering, pp.2244-2257.
Holman, R.A., and Sallenger, A.H. (1985). Setup and swash on a natural beach. J. Geophys. Res., 90: 945-953.
Holland, G.J., Lynch, A.H. and Leslie, L.M. (1987) Australian East-Coast Cyclones. Part 1: Synoptic Overview and Case Study. Mon. Wea. Rev., 115, 3024-3036.
Janssen, V and Haasdyk, J (2011). Assessment of network RTK performance using CORSnet-NSW. Intl Global Navigation Satellite Systems Society IGNSS Symposium, 15-17 Nov, Sydney.
Lord D.B. and Kulmar M.A. (2000), "The 1974 Storms Revisited: 25 years Experience in Ocean Wave Measurement Along the South-East Australian Coast†, Proceedings International Conference of Coastal Engineering, pp 559-572, ASCE.
McHendrie, G., (1988). SDSZ - A Program for Sediment Size Analysis: U.S. Geological Survey. Branch of Pacific Marine Geology, Menlo Park, CA.
NSW Govt (1990). Coastline management manual, September 1990, ISBN 0730575063.
PWD (1985). Elevated Ocean Levels Storms Affecting the NSW Coast 1880-1980. PWD Coastal Branch Report No. 85041.
PWD (1986). Elevated Ocean Levels Storms affecting the NSW Coast 1980-1985. PWD Coastal Branch Report No. 86026.
Rodríguez, J.G., and Uriarte, A. (2009). Laser Diffraction and Dry-Sieving Grain Size Analyses Undertaken on Fine- and Medium-Grained Sandy Marine Sediments: A Note. Journal of Coastal Research, Vol. 25, No. 1, pp. 257-264.
Short A.D. (2007). Beaches of the New South Wales Coast (2nd edition). 1-920898-15-8. Sydney University
Short, A.D. and Trenaman, N.L. (1992). Wave Climate of the Sydney Region, an Energetic and Highly Variable Ocean Wave Regime. Aust. J. Mar. Fresh Res., 1992, 43, 765-791.
Syvitski, J.P.M. (2007). Principles, Methods and Application of Particle Size Analysis. Cambridge University Press. 388 pages.
Wright, L.D., and Short, A. D (1984). Morphodynamic variability of surf zones and beaches: A Synthesis: Marine Geology, 56:93-118.
Xu, R., and Di Guida, O.A. (2003). Comparison of sizing small particles using different technologies. Powder Technology, Vol. 132, pp. 145- 153.
You, Z. J (2011). Extrapolation of historical coastal storm wave data with best-fit distribution function. Australian Journal of Civil Engineering, 9: 73-82.
You, Z. J., Nielsen, P., Hanslow, D and Pritchard, T (2012). Elevated water levels at trained and untrained river entrances on the east coast of Australia. International Conference on Coastal Engineering, 1-6 July, Santander, Spain.
You, Z. J and Nielsen, P (2013). Chapter 22: Extreme coastal waves, ocean surges and wave runup. Coastal Hazard Book edited by Charles W Finkl, Coastal Research Library 6, Springer Publisher.