Perth’s Three Coasts
To understand Perth’s ‘deep structure’ is to understand Perth as a Wet City, above and below. The water that persists in the contemporary city can be conceived as Three Coasts, provoking a reorientation of the city to its water systems.
The Three Coasts also enable a categorisation of Perth into broad environmental types in relation to urban heat, breeze, rainfall, vegetation, ecology, soil type and geology. This reveals significant environmental variation across the Swan Coastal Plain from Indian Ocean to Darling Scarp. These environmental types are important in informing building and planning responses to the conditions of the city. Such classifications and distinctions can also be helpful in comprehending a broader condition and context. This is some preliminary work defining Perth’s Three Coasts.
The First Coast is the sand and limestone coast at the Indian Ocean. Perth’s urban form is oriented to this First Coast and sprawls along it.
The Second Coast is formed by the chains of wetlands that run parallel to the coast, formed by the interdunal depressions where the groundwater mounds surface.
The Third Coast is the marshy and clayey high groundwater plain at the foothills of the Darling Scarp, Semeniuk (1987) called this the palusplain. Much of Perth’s projected urban sprawl is projected to occur in this region.
This borrows from the work of Rod Simpson and the Greater Sydney Commission in defining Three Cities of Sydney, as well as the ‘Third Coast’ idiom used in the USA to refer to the Great Lakes region, adopted by the recent Third Coast Atlas.
