Swan Coastal Plain

Coordinates: 31°49′S 115°50′E / 31.82°S 115.84°E / -31.82; 115.84
Source: Wikipedia, the free encyclopedia.

Swan Coastal Plain
Swan Coastal Plain scrub and woodlands
Southwest Australia woodlands
Geography
Area15,280 km2 (5,900 sq mi)
CountryAustralia
StateWestern Australia
Coordinates31°49′S 115°50′E / 31.82°S 115.84°E / -31.82; 115.84
Conservation
Conservation statusCritical/endangered[1]

The Swan Coastal Plain in Western Australia is the geographic feature which contains the Swan River as it travels west to the Indian Ocean. The coastal plain continues well beyond the boundaries of the Swan River and its tributaries, as a geological and biological zone, one of Western Australia's Interim Biogeographic Regionalisation for Australia regions.[2][3] It is also one of the distinct physiographic provinces of the larger West Australian Shield division. [4] [1]

Location and description

The coastal plain is a 30-kilometre-wide (19 mi) strip on the Indian Ocean coast directly west of the

Canning
.

The sediments of the Perth Basin are Tertiary and Quaternary in age immediately below Perth and include coquina, travertine, and sandy limestones with abundant shelly material. Perth is sited on a set of sand dunes formed during the Pliocene-Pleistocene during the last ice age. Offshore, the sand dune system and surficial deposits transition into a system of partly eroded limestones and sandy limestones. These form a series of drowned cuestas which today form submerged reefs.

Because of the steepness and orientation of the Darling Scarp, watercourses run off the scarp in a westerly direction. On reaching the Swan Coastal Plain, they encounter two obstacles: firstly, the high permeability of the soil results in the loss of much water. Much flow is lost, and some watercourses simply cease to flow, for example,

Peel Inlet
.

Coastal dunes and Wanneroo wetlands

The dune topology also results in extensive north-to-south-oriented chains of wetlands, again located in the swales. For example, the chain of lakes north of Perth includes lakes of the Wanneroo wetlands including – Lake Pinjar, Jandabup Lake and Gnangara Lake. The large bodies of water in the estuary of the Swan River, Perth Water and Melville Water are also located in dune swales.

Geology

The Swan coastal plain is characterised by a series of sand dune systems, the Quindalup dunes, the Spearwood dunes, and the Bassendean dunes, which run from west to east (in increasing age) from the coastline to the major faults which form the eastern boundary of the plain.

Bullsbrook, and to the south by the Collie-Naturaliste Scarp.[6]
The Pinjarra plain lies between the Bassendean dunes and the eastern scarps.[7] Early work on all three dune systems considered them to have been formed at differing times by the deposition of sands carried by wind (aeolian and/or by river processes (fluviatile).[6][8] More recently, later authors have argued that these sandplains are mostly the product of in situ weathering.[9][10]

The carbonate material of all three dune systems has been completely leached, leaving dunes which consist solely of quartz sand.[8] Within the Spearwood dunes, the yellow or grey sand may be several metres thick.[8]

The dune systems have been much studied, as the water retained within them supplies much of Perth's water needs. (See Gnangara Mound).

Climate

In the southwest of Australia, the Nyoongar seasonal calendar includes six different seasons in a yearly cycle. These are Birak, Bunuru, Djeran, Makuru, Djilba and Kambarang. Each of the six seasons represents and explains the seasonal changes we see annually. The flowering of many different plants, the hibernation of reptiles and the moulting of swans are all helpful indicators that the seasons are changing.

The Nyoongar seasons can be long or short and are indicated by what is happening and changing around us rather than by dates on a calendar. Aligning Nyoongar seasons with Western calendar months can provide an overview of a typical year.

This six season calendar is extremely important to Nyoongar people, as it is a guide to what nature is doing at every stage of the year, as well as understanding respect for the land in relation to plant and animal fertility cycles and land and animal preservation.

The south west region of Western Australia was one of the first places on earth to experience the effects of human induced climate change, namely a significant decline in annual rainfall. The drying climate is expected to continue and exacerbate bushfires. The summer of 2021/22 has been the hottest on record, with many consecutive days over 40 degrees Celsius.

Ecology

The Swan Coastal Plain is a specific botanical province.[11][12]

Flora

Southwestern Australia is very rich in flora, with an estimated 8,000 species, a quarter of which can be found on this coastal strip. The traditional flora of the dunes and the fairly infertile plain was dense shrubby kwongan heathland adapted to the poor soils, dry summers, and regular fires. Kwongan vegetation contains a large number of endemic plant species, especially shrubs and wildflowers, including yellow flame and toothbrush grevilleas, fan-flowers, and cockies' tongues. The heath is scattered with woodland of Banksia and other trees including the red-blossomed quandong (desert peach) and firewood banksia. Going further inland, especially in river valleys where the soil is better, eucalyptus woodlands including tuart (Eucalyptus gomphocephala) occur. The wetlands meanwhile have been particularly important ecologically, supporting a rich habitat of many plant varieties.

The Swan Coastal Plain is a particularly important centre for certain types of plants, including Banksia, but also

Christmas tree
.

Fauna

The coastal plains are home to a number of marsupials from the large

southwestern pygmy possum and mouse-like honey possum. Remnant populations of some marsupials are found on offshore islands including the Tammar wallaby and the quokka, the latter particularly on Rottnest Island. The coastal plains skink
, discovered in 2012, is endemic to sand dunes in the area, and is threatened by residential development.

Threats and preservation

Much of the plain has been cleared for agriculture and urban development, especially in and around Perth, where the heath has been almost entirely cleared as far as the Darling Scarp and the city is spreading up and down the coast. Although some areas are protected, clearance is going on while the plant disease

Bold Park, Whiteman Park, Kensington Bushland and Thomsons Lake
.

History

Traditionally, this area was under the care and control of the Yued,

old growth forests
observed at the time of first contact. At this time, the kwongan heathland was much more widespread along the coast.

In the 1830s, it was originally named Great Plain of Quartania or Plain of Quartania by James Stirling, the first governor of Western Australia, but those terms have fallen into disuse.

European settlement led to many of the wetlands areas being drained for land reclamation to take advantage of the fertile soil for farming enterprises, and for expansion of parks and recreation areas. The city of Perth sits on an area of reclaimed wetlands. Between 49% (Riggert, 1966) and 80% (Godfrey, 1989) of the wetlands on the coastal plain is thought to have been drained, filled, or cleared since 1832. Lake Monger and Herdsman Lake are the last two major wetlands remaining in close proximity to the city.

Lake Monger was originally part of a

Herdsman Lake made up what was known as "The Great Lakes District". Other lakes and swamps in the immediate northern vicinity of the early Perth township were Lake Kingsford (site of the current Perth railway station), Lake Irwin (Perth Entertainment Centre
) and further north were Stone's Lake (Perth Oval), Lake Poullet (First Swamp, part of what is now Birdwood Square), Lake Thomson (Mews Swamp, between Lake, Brisbane, and Beaufort Streets) and Lake Henderson (parts of what is now Robertson Park and Dorrien Gardens). Further north still lay Second Swamp (Bulwer Street, east of Lake Street), Third Swamp (Hyde Park), and Three Island Lake and Smith's Lake (now Charles Veryard Reserve). Many of these lakes formed a natural interconnected drainage system which found its way into the Swan River at East Perth through Claise Brook. In 1833, water draining from Lakes Kingsford, Irwin, Sutherland, and Henderson was used to drive a water-driven mill located in Mill Street.

See also

  • Islands of Perth, Western Australia

References

  1. ^ a b "Swan Coastal Plain scrub and woodlands". The Encyclopedia of Earth. Retrieved 20 August 2021.
  2. Australian Government. Archived from the original
    on 5 September 2006. Retrieved 31 January 2007.
  3. ^ IBRA Version 6.1 data
  4. ^ "Swan Coastal Plain scrub and woodlands". Digital Observatory for Protected Areas. Retrieved 20 August 2021.
  5. S2CID 54499926
    .
  6. ^ a b McArthur, W.M, Bettenay, E, 1974. The development and distribution of the soils of the Swan Coastal Plain. Soil Publication No. 16. C.S.I.R.O.PDF
  7. ^ Broun, L. (2004), Banksia Woodland resilience to groundwater drawdown on ohe Gnangara Mound, Edith Cowan University, Research Online, Perth, Western Australia, retrieved 20 August 2018
  8. ^ a b c R.B. Salama, D.W. Pollock, J.D. Byrne and G.W. Bartle. 2000. Geomorphology, Soils and Landuse in the Swan Coastal Plain in relation to Contaminant Leaching, Agrochemical Pollution of Water Resources, Proceedings of a Conference held on 16–18 February 2000 at Hat Yai, Thailand, Australian Centre for International Agricultural Research, Canberra 2001, pp. 105-117.
  9. S2CID 129686726
    .
  10. ISSN 0812-0099
    .
  11. ISBN 0-642-21371-2
  12. ISBN 0-646-40100-9

Further reading
Wikimedia Commons has media related to Swan Coastal Plain.

External links

Maps: Australia's bioregions IBRA 5.1

IBRA 6.1 Explorer

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