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Summary regional descriptions of the Australian coast

Davies (1986) undertook a systematic description of the physical characteristics of Australian coasts which has not been superseded. Davies divides Australia's coastal landforms into four regions, based on:

• climate (particularly as it affects run-off)

• geological history (as it affects outcrop, landform and sediment supply)

• oceanographic variables (tide, width and slope of continental shelf, and wave climate).

The regions are termed 'Warm Temperate Humid', 'Warm Temperate Arid', 'Tropical Arid', and 'Tropical Humid' (figure 2.8). Table 2.2 summarises Davies description and adds data from a variety of sources.

A typology of coasts by LOICZ

The classifications discussed above have been developed by expert opinion: experts in coastal processes have evaluated the available data and then synthesised it to give a classification and description of the Australian coast.

The Land-Ocean Interactions in the Coastal Zone (LOICZ) project of the International Geosphere-Biosphere Program (IGBP) has taken a different approach. It has sought to establish a typology of coasts (that is, an analysis or classification based on types). This typology focuses on carbon, nitrogen and phosphorus (CNP) fluxes in all parts of the global coastal zone. The process has been to assemble existing data, such as run-off, evaporation, tidal range and wave climate, and then to cluster for 0.5° (latitude and longitude) points. Clustering has been accomplished using traditional methods (LOICZ 2002); in this case, vector quantification has been used. Data clusters have been calibrated with published CNP budgets to establish a typology of coastal nutrient flux. This is being generalised to areas where CNP budget information is not available in detail.

The methodology has been tested in Australia, at a clustering of 1° (Bud- demeier & Maxwell 2000), giving a mapped result similar to the classification developed by expert opinion, above. Further refinement of this method appears to be capable of providing a more detailed classification of the coast, using methods that may be replicated. Clearly it has the potential to isolate significant coastal descriptors which can best be used to typify CNP flux, and hence bio- geochemical activity, at the coast.

Region

Characteristic

Warm Temperate Humid

Warm Temperate Arid

Tropical Arid

Tropical Humid

Continental Shelf [Inner shelf gradient]

Narrow, steeply sloping.

Medium to narrow; varied gradients. Quaternary dunes give complex shelf topography, with many submerged, partly submerged reefs

Wide, shallow, gently sloping

Wide, gently sloping

Tides

Microtidal; springs < 2.0 m.

Microtidal; springs < 2.0 m. larger tides in gulfs

Large tidal range

Large-medium tidal range

Storms

Depressions; cyclones as far south as the Gold Coast

Depressions; surge significant in Gulfs

Cyclones (10-15 per decade). Surge important on all coasts

Cyclones

Waves

Swell s-e., 2-3 m; local n-e. chop

Swell s-w., 2-4 metres; high energy on open coast

Low energy (except cyclonic episodes)

Low energy: tropical + reef sheltering (except cyclonic episodes)

Winds

(all regions show marked sea/land breeze variation)

Strong w. component in winter. Variable in summer, with marked afternoon sea breeze

Very strong w.-s-w. component in winter; s.-s-e. in summer; sea breeze important to nearshore processes

Dominant e. component in winter; strong w. component in summer

Very dominant and strong e.-s-e. component in winter; w.-n-w. in summer

Geology

Mesozoic uplift of igneous and sediments of eastern highlands

Variety of structural basins; faulting [rarrow] plan shape. Stable Quaternary limestone plain on w. coast

Quaternary sediments including Pleistocene low sea level desert dunes

Highly varied

Landforms

Mainly zeta-curve beaches w. headlands. High tide platforms on cliffed sections. Varied coastal plain topography

Varied, with many aeolianite cliffs, platforms and headlands. Tidal low plains in Gulfs. W. coast dominated by aeolianite dune ranges and corridors

Mainland beach coast with some barrier development. Many islands (1st.) and coral reefs offshore

Varied. Beach + headl. behind reef on e. Qld. coast; low muddy coastal plains in NT. Extreme low gradient shores of mangrove, saltmarsh and Cheniers in Gulf of Carpentaria

Run-off

Annual ave 5 cm. Most large discharges 30-150 m3/s

Seasonal only; negative annual water budget

No run off

Large water + sediment discharge, seasonal rhythm

Beach materials

medium-fine siliceous sands; littoral drifts, to n., including during Pleistocene low sea levels. Pleistocene barriers with beachrock

Mainly marine calcareous origin, some siliceous; fine-medium grade sands. Large quantities

mainly calcareous, low gradient beaches/extensive tidal plains

Muds in north and Gulf. Fine-coarse sands in e. Qld; only region of Australia where large quantities of sediments are delivered to coast

Dunes

Multiple beach ridges at Pleistocene and Holocene high sea level. Storage at n. end of bays. Long-term accumulation in sand masses of s. Qld

Large Pleistocene dune fields lithified [rarrow] aeolianite

Low (<10 m) dunes (+ low lithified barriers); dune development on coastal plain backed in places by desert dunes

Large mainland sand masses north of Qld's east coast rivers

Estuaries

Wetlands

Many flooded deep channels; some blocked with barriers and filled; normal and reverse deltas Saltmarsh grasses; 1-4 mangrove species

Rare, except small estuaries of s-w. WA, due to lack of run-off

Samphire saltmarshes in gulfs and sheltered bays. Remnant stands of Avicennia marina

None

Estuaries buried by sediments [rarrow] deltas in Qld. Extensive narrow estuaries and plains in NT < 30 species of mangrove. Mangrove + tall grass floodplains of NT

Sources: Davies (1986), with additions from Atlas of Australian Resources (1980-90), Bureau of Meteorology (1989), Gill (1982), Radok (1976).

Figure 2.9 The following set of photographs has been chosen to illustrate the variety of coastal types of the Australian continent, as well as something of the variety of resource use discussed later in this book

The following set of photographs has been chosen to illustrate the variety of coastal types of the Australian continent, as well as something of the variety of resource use discussed later in this book

Conclusion

Australia's coast is varied and dynamic. As table 2.2 suggests, combinations of differing geological, climatic, oceanographic and biotic factors give great contrasts in coastal environments. These combinations can be regionalised to some extent, largely on the basis of climate and wave energy. Coastal management in Australia takes place within a series of varied and dynamic environments. From the Top End to Tasmania there is great pressure of uses: everywhere in the varied coastal environments, management is complex, challenging, and needed.

 
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