A Landsat TM and ETM+ survey of quaternary coastal landforms in the central coast of NSW, Australia

Julia Yagüe., Mª Pilar García, Mª Eugenia Pérez
Complutense University of Madrid, Department of Regional Geographical Analysis and Physical Geography
Avd. Prof. Aranguren s/n. 28040 Madrid, Spain

ABSTRACT

Landsat TM and ETM+ images are analysed to define and describe the vast array of quaternary landforms and sediments that occur in the Great Lakes district of the central coast of New South Wales (Thom, 1981) (West, 1985) , Eastern Australia, about 230 km north of Sydney. The study area falls between the lower Hunter river mouth to the south (Newcastle) and Cape Hawke Harbour in Wallis Lake to the north (Forster Tuncurry). Field campaigns preceded the remote sensing survey.

The geological structure and the physiography of the area is controlled by folds which tend from due north to N40ºW; the resistance of the carboniferous and permian strata to erosion determine the coastal landforms of quaternary age. Several eolian, erosive and cumulative coastal landforms can be recognized within the bedrock embayments, which are the product of fluvial, paludal, lacustrine, estuarine and marine processes. Quaternary climatic oscillations have largely determined the geomorphic progression of the area in two distinct and parallel beach ridge systems. Landsat imagery helped to identify the dimensions of the following features: (i) Hard rock headlands and volcanic outcrops that conform the turning point of embayments. (ii) Flood plain deposits, including forms such as levees, back-swamps and filled-in channels. (iii) Estuaries and deltas. (iv) Eustatic terraces, although these are found further inland from the actual coastline. (v) Coastal lagoons (locally called lakes) enclosed by barriers. Size and shape vary depending on bedrock depth and relationship to barrier system. Bathymetry, hydrology and salinity do not follow a uniform pattern throughout the lagoons. (vi) Bogs and swamps, evidencing the existence of past larger water bodies, now colonized by vegetation fringing the lagoons’ inner bays or silting the low inner barrier corridors. (vii) A double barrier system of sand ridges; the inner barrier system is composed of Pleistocene sands while the outer barrier consists of Holocene sands. (viii) Sand spits, enclosing coastal lagoons or linking offshore rocky outcrops.

Analysis methods included image geocorrection and mosaicing, atmospheric filtering, radiometric enhancement, visual interpretation, supervised classification and mapping. The multitemporal analysis provided by the various image dates (TM 30.11.1993; ETM+ 08.08.2001) helps to evidence the active dynamics of these environs. Recent multitemporal RS research has been carried out in this area (Wallis Lake) by Anstee , combining multispectral and hiperspectral datasets for mapping seagrass and macro-algae coverage.

REFERENCES

1. Thom, B. G., Bowman, B. G., & Roy, P. S. (1981). Late Quaternary evolution of coastal sand barriers, Port Stephens-Myall Lakes area, central New South Wales, Australia. Quaternary Research, 15(3), 345-364.
2. West, R.J., Thorogood, C., Walford, T., & Williams, R.,J (1985) An estuarine inventory for New South Wales, Australia. Department of Agriculture, NSW.
3. Anstee, J. M., Dekker, A.,G., & Brando, V.E., (2004) Retrospective change detection in a shallow coastal tidal lake: mapping seagrasses in Wallis Lake, Australia. In Series in Remote Sensing. Analysis of multitemporal remote sensing images. (P. Smits & L. Bruzzone, Eds.) Vol III Proceedings of the Second International Workshop on the Analysis of Multi-Temporal Remote Sensing Images, JRC, Ispra, Italy 16-18 July 2003.277-285.

Last Update: 2005-03-16