Perth
Perth
1972 - 1988
Perth is a strikingly beautiful city to be in and equally fascinating to
view from space. It is a dynamic city both in political and economic lifestyle.
The promotional logo once used by tourist agencies was - 'Relax in a state
of excitement'.
There are other more substantial indications why we can expect to find change in and around the city of Perth. The first is that the population of Western Australia is growing at a high rate. It has increased from ~ 1 054 000 in 1971 to 1 586 000 in 1991. That is an increase (relative to 1971) of a staggering 50%, giving an average annual increase of 2.5%. The second is that Perth - like Adelaide - contains about 75% of the state population. Perth and Adelaide are second only to Canberra in the city-state rank. The proportion of the state population residing within the city of Perth has increased only slightly in the last twenty years. As the state has grown, so also has Perth.
We have available Landsat images to look back over a period of 14 years; from January 19, 1974 to December 20, 1988. The changes that we will find are very interesting indeed. Some changes from the Perth area you will have already seen in an earlier Chapter.
Three Landsat FCC images of Perth: January 19, 1974; December 20, 1988; and the 1974-1988 Difference.
Use your browser to open each image in a new window to compare them.
The Perth urban area straddles the interesting shape of the Swan River and appears evenly divided by it. It is bounded in the east by the still mostly wooded Darling Range and in the west by the Indian Ocean. The southern edge of our scene is Kwinana and the northern edge is Wanneroo Beach. Apart from the uplands of the Darling Range, the landforms of the remainder of the scene are flat to gently undulating plains, the Swan Coastal Plain. These landforms offer no constraint to the endless expansion of residential suburbs.
The history of the establishment and expansion of the first European settlement along the Swan River can be read in the spectral and spatial pattern of urban spread. Almost all the pre-settlement landcover in this scene has been altered in some way by human activities. Much of the Swan coastal plain with its complex array of sand dunes has been cleared of eucalypt woodland and heath, and many large wetlands, eg Forestdale Lake, have been significantly altered. Parts of the jarrah forests on the uplands of Darling Ranges have been cleared for agriculture, Urbanisation and some plantation forestry. You can interpret that most of the clearing for agriculture has continued as high up to the footslopes as was possible.
Even with all the obvious landcover change indicated by imposed straight lines and boundaries, there remains at least 30% of the original vegetation in this scene. This is less than Brisbane but more than Sydney, Melbourne, or Adelaide.
The spectral information contained within the Perth scenes is rich and informative. The Perth and Fremantle CBD, the ice-blue of concrete and asphalt, is much the same as all cities. The contrast lies in its close neighbour to the west, King's Park, which with its dense covering of native vegetation appears as a dark island in a sea of pink suburbia. The urban spread has this spectral signature characteristic of green actively growing vegetation because the suburbs are well covered with lawns and street trees, both exotic and native. In the middle of a hot January in 1974, the suburbs of Perth are green and luxuriant, no doubt resulting from the extensive use of groundwater for domestic watering. The prominent circular wetland north of the CBD, Herdsman Lake, is either nearly dry or completely covered in wetland vegetation because it has the signature of green vegetation.
The nature of the remaining landcover in this scene can be identified by both its spectral and spatial characteristics. The dark landcover in top centre can be identified by the regular road grid as plantation forestry. The cream-yellow patchwork is agricultural landcover, regular paddocks of mostly pastures with some cropping, that is dry and hayed-off.
The size of the urban area is considerable. Perth is a low density city. Only 20% of urban housing is classified as medium density (flats, apartments, etc). The suburbs are predominantly (80%) detached housing; one per allotment surrounded by garden. The spatial pattern of urban spread is obviously related to the pattern of road transport; the freeways are blue lines through the pink suburbs. However, the pink colour, characteristic of low density house and gardens, changes little from the edges of the CBD to the outliers where it changes abruptly to the signature of dry rainfed agricultural landcover. Perth is a Car City.
There are obvious changes in the landcover of the Perth urban area between January 1974 and December 1989. The most obvious is a spectral shift. The whole area in 1989 has a more reddish colour, indicating that most of the vegetation is greener or growing more actively than it was in 1974. These seasonal and temporary changes are not our focus. Permanent human-made changes are apparent just by eyeball comparison of the 1974 and 1989 scenes. The 1989 scene appears more 'busy'. There is more spatial pattern in the landcover.
The location and size of these changes are clearly seen on the Difference FCC image. The conversion of landcover by clearing, the dark signature, rings the city to north and south and to the east of Fremantle. Perth, of all the cities examined so far, shows the most extensive and compact areas of urban expansion. Some of this change is associated with urban infill: the building of Murdoch University south of the Swan River is just one example of this change within the boundaries of established suburban areas. Also, within this scene there are landcover changes associated with agriculture and forestry. However, they appear to be small relative to those resulting from urban expansion. In addition, there are many other interesting changes that have been flagged in the Difference FCC image: changes in wetlands; the filling of new reservoirs; and the construction of roads.
In summary
Perth is the capital of a state with the highest rate of population growth in Australia. Perth is the focus of that growth because it contains over 70% of the entire state population. Perth is on the Swan Coastal Plain, a landform that offers no constraint to the expansion of residential housing. That appears to be the pattern of growth that has occurred. The changes in Perth that can be detected from space over the last 14 years are the most dramatic we have found so far. Perth is perhaps the best, or worst example of a Car City in Australia.
