The Swan Coastal Plain in

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to t ...

is the geographic feature which contains the Swan River as it travels west to the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by ...

. 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 The Interim Biogeographic Regionalisation for Australia (IBRA) is a biogeographic regionalisation of Australia developed by the Australian government's Department of Sustainability, Environment, Water, Population, and Communities. It was deve ...

(IBRA) regions.IBRA Version 6.1
data It is also one of the distinct physiographic provinces of the larger West Australian Shield division.

Location and description

The coastal plain is a strip on the Indian Ocean coast directly west of the

Darling Scarp The Darling Scarp, also referred to as the Darling Range or Darling Ranges, is a low escarpment running north–south to the east of the Swan Coastal Plain and Perth, Western Australia. The escarpment extends generally north of Bindoon, to ...

uplands running from Cape Naturaliste in the south to north of the city of

Perth Perth is the capital and largest city of the Australian state of Western Australia. It is the fourth most populous city in Australia and Oceania, with a population of 2.1 million (80% of the state) living in Greater Perth in 2020. Perth is ...

. The plain mainly consists of fairly infertile sandy soil along with coastal sand dunes, river estuaries, and a number of wetlands kept back from the sea by the dunes. A number of rivers cross the plain from east to west from the Darling Scarp towards the sea, including the Swan and its main tributary, the Canning. The sediments of the Perth Basin are Tertiary and Quaternary in age immediately below Perth and include

coquina Coquina () is a sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically sorted fragments of the shells of mollusks, trilobites, brachiopods, or other invertebrates. The term ''coquin ...

travertine Travertine ( ) is a form of terrestrial limestone deposited around mineral springs, especially hot springs. It often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and even rusty varieties. It is formed by a p ...

, 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 An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gre ...

. 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, Wungong Brook, Cardup Brook, and Manjedal Brook. Secondly, the sequence of north-to-south-oriented dunes create obstacles to further westerly flow. Many watercourses turn at right angles and flow south or north along the dune swales, and in some cases this allows multiple watercourses to coalesce. For example, on reaching the coastal plain, Ellen Brook runs south for around , picking up a number of watercourses along the way, before finally emptying into the Swan River. Another example is the Serpentine River, which runs west to less than from the coast, then turns south, running parallel with the coast for nearly before disgorging into 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 The Wanneroo wetlands are a series of wetlands, swamps and lakes that occur on the Swan Coastal Plain of Perth, Western Australia. They are linked very closely to the Gnangara Mound. They are in part, incorporated into the Yellagonga Regiona ...

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. The plain is bounded to the east by the

, to the north by a subsidiary fault running north-west from Bullsbrook, and to the south by the Collie-Naturaliste Scarp. The Pinjarra plain lies between the Bassendean dunes and the eastern scarps. 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).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. More recently, later authors have argued that these sandplains are mostly the product of in situ weathering. The carbonate material of all three dune systems has been completely leached, leaving dunes which consist solely of quartz sand. Within the Spearwood dunes, the yellow or grey sand may be several metres thick. The dune systems have been much studied, as the water retained within them supplies much of Perth's water needs. (See

Gnangara Mound The Gnangara Mound is an area north of Perth, Western Australia where a large mound of sandy soil reaches an elevation of about . It stores about of fresh water, about one hundred times Perth's current annual water usage. It is currently the si ...

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.Paczkowska, Graznya and Chapman. Alex R. ''The Western Australian flora: a descriptive catalogue'' Wildflower Society of Western Australia, Western Australian Herbarium, CALM, and the Botanic Gardens & Parks Authority, Perth. 2000.

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 Kwongan is plant community found in south-western Western Australia. The name is a Bibbelmun (Noongar) Aboriginal term of wide geographical use defined by Beard (1976) as Kwongan has replaced other terms applied by European botanists such as ...

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 ''Eucalyptus'' () is a genus of over seven hundred species of flowering trees, shrubs or mallees in the myrtle family, Myrtaceae. Along with several other genera in the tribe Eucalypteae, including '' Corymbia'', they are commonly known as ...

woodlands including tuart ''(

Eucalyptus gomphocephala ''Eucalyptus gomphocephala'', known as tuart, is a species of tree, one of the six forest giants of Southwest Australia. Tuart forest was common on the Swan coastal plain, until the valuable trees were felled for export and displaced by the urb ...

)'' 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 ''

Caladenia ''Caladenia'', commonly known as spider orchids, is a genus of 350 species of plants in the orchid family, Orchidaceae. Spider orchids are terrestrial herbs with a single hairy leaf and a hairy stem. The labellum is fringed or toothed in most s ...

'' orchids and '' Leucopogon'' shrubs, indeed some genera, such as the ''

Dryandra ''Banksia'' ser. ''Dryandra'' is a series of 94 species of shrub to small tree in the plant genus ''Banksia''. It was considered a separate genus named ''Dryandra'' until early 2007, when it was merged into ''Banksia'' on the basis of extensi ...

'' series of ''Banksia'' and the ''

Synaphea ''Synaphea'' is a genus of small shrubs and is Endemism, endemic to Western Australia. Synapheas have variably shaped leaves but consistently yellow flowers with an unusual pollination mechanism. Description Plants in the genus ''Synaphea'' are ...

'' flowers are found nowhere else in the world. Other flora of the plain includes a type of mistletoe called the

Christmas tree A Christmas tree is a decorated tree, usually an evergreen conifer, such as a spruce, pine or fir, or an artificial tree of similar appearance, associated with the celebration of Christmas. The custom was further developed in early modern ...

Fauna

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

western grey kangaroo The western grey kangaroo (''Macropus fuliginosus''), also referred to as a western grey giant kangaroo, black-faced kangaroo, mallee kangaroo, sooty kangaroo and (when referring to the Kangaroo Island subspecies) Kangaroo Island grey kangaroo, is ...

to the very small

southwestern pygmy possum The western pygmy possum (''Cercartetus concinnus''), also known as the southwestern pygmy possum or the ''mundarda'', is a small marsupial found in Australia. Genetic studies indicate its closest relative is probably the eastern pygmy possum, f ...

and mouse-like

honey possum The honey possum or noolbenger (''Tarsipes rostratus''), is a tiny species of marsupial that feeds on the nectar and pollen of a diverse range of flowering plants. Found in southwest Australia, it is an important pollinator for such plants as '' ...

. Remnant populations of some marsupials are found on offshore islands including the Tammar wallaby and the quokka, the latter particularly on

Rottnest Island Rottnest Island ( nys, Wadjemup), often colloquially referred to as "Rotto", is a island off the coast of Western Australia, located west of Fremantle. A sandy, low-lying island formed on a base of aeolianite limestone, Rottnest is an A-cla ...

. The

coastal plains skink The coastal plains skink (''Ctenotus ora'') is a species of skinks, found on the Swan Coastal Plain south of Perth, Western Australia. Taxonomy The species was identified in 2012 by researchers from Australian National University, who were con ...

, 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 '' Phytophthora''

dieback Dieback may refer to a number of plant problems and diseases including: * Forest dieback caused by acid rain, heavy metal pollution, or imported pathogens * The death of regions of a plant or similar organism caused by physical damage, such as from ...

and changes to traditional fire regimens affect the heathland vegetation including the ''Banksia'' trees. Protected areas include Kings Park, Beeliar Wetlands,

Star Swamp Star Swamp Bushland Reserve is a bushland reserve occupying about half of the land area of the suburbs of Watermans Bay and North Beach in the northern suburbs of Perth, Western Australia. The precise origin of the name is unknown, but the ea ...

Hepburn Heights Bushland Hepburn may refer to: Surname People with the surname Hepburn (the most famous in recent times being actresses Katharine Hepburn and Audrey Hepburn): * Hepburn (surname) Linguistics * Hepburn romanization, a system for the romanization of Japa ...

Canning River Regional Park The Canning River Regional Park is the largest of eight regional parks within the Perth metropolitan area. The park covers approximately on both sides of the Canning River between the bridges carrying Nicholson Road and Leach Highway over th ...

Bold Park Bold Park is a urban bushland area in the suburb of City Beach, in Perth, Western Australia. It is located directly west of the Perth central business district, its western border less than one kilometre from the Indian Ocean. To the east, ...

, Whiteman Park, Kensington Bushland and

Thomsons Lake Thomsons Lake Nature Reserve is a lake nature reserve around Thomsons Lake (Noongar: ''Jilbup'') in the City of Cockburn, Western Australia, approximately south of the central business district of Perth, the state capital, and on the southe ...

History

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

Binjareb The Bindjareb, Binjareb, Pindjarup or Pinjareb are an Indigenous Noongar people that occupy part of the South West of Western Australia. Name It is not clear if ''Pindjarup'' is the historically correct ethnonym for the tribe. After their dis ...

, and Wardandi

Noongar The Noongar (, also spelt Noongah, Nyungar , Nyoongar, Nyoongah, Nyungah, Nyugah, and Yunga ) are Aboriginal Australian peoples who live in the South West, Western Australia, south-west corner of Western Australia, from Geraldton, Western Au ...

peoples, whose hunter-gathering firestick farming practices maintained the climax vegetations

old growth forests An old-growth forestalso termed primary forest, virgin forest, late seral forest, primeval forest, or first-growth forestis a forest that has attained great age without significant disturbance, and thereby exhibits unique ecological featu ...

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 Herdsman Lake ( nys, Njookenbooro), also known as Herdsmans Lake, is a freshwater lake located on the Swan Coastal Plain, north-west of Perth, Western Australia, in the suburb of Herdsman. The main shared use path around the lake is approxima ...

are the last two major wetlands remaining in close proximity to the city. Lake Monger was originally part of a series of freshwater wetlands running north from the Swan River along the coastal plain for about . Lake Monger with Georgiana Lake and Lake Sutherland (both near

Mitchell Freeway The Mitchell Freeway is a freeway in the northern suburbs of Perth, Western Australia, linking central Perth with the city of Joondalup. It is the northern section of State Route 2, which continues south as Kwinana Freeway and Forrest High ...

, near Sutherland and Newcastle streets) and

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 Perth railway station is the largest station on the Transperth network, serving the central business district of Perth, Western Australia. It serves as an interchange between the Airport, Armadale, Fremantle, Joondalup, Mandurah and Midland ...

), Lake Irwin (

Perth Entertainment Centre The Perth Entertainment Centre was an indoor arena and cinema complex in Perth, Western Australia, located on Wellington Street at the northern edge of the Perth central business district. It was demolished as part of the Perth City Link proje ...

) 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.

References

External links

* Maps: Australia's bioregions IBRA 5.1 * http://www.environment.gov.au/parks/nrs/science/bioregion-framework/ibra/index.html IBRA 6.1 Explorer * http://www.environment.gov.au/metadataexplorer/explorer.jsp
– an online version of Thackway and Cresswell
{{Physical geography topics IBRA regions Mediterranean forests, woodlands, and scrub in Australia Physiographic provinces Plains of Australia Southwest Australia