Let's start our examination of the other state capitals with the city of Sydney. Sydney is the most populous city in the most populous state of Australia. The population of New South Wales has grown by 21% during 1971-1991. However, the relative distribution of population within and without Sydney has declined slightly from 64% in 1971 to 62% in 1991; in other words the growth in population of New South Wales was slightly greater outside Sydney. The location of much of this growth is the coastal strips of Northern New South Wales; see later in this Chapter.
The two satellite images that we will use allow us to look back over seventeen years; from October 18, 1989 back to December 11, 1972.
Three Landsat FCC images of the city of Sydney: December 11, 1972; October 18, 1989 and the 1972-1989 Difference.
Use your browser to open each image in a new window to compare them.
The Sydney urban area is much larger than these images. However, because of the limitation in the availability and location of the 1972 images, not all the Sydney urban area was captured. What we have to work with is a polygon beginning with Bundeena in the south to Broken Bay in the north, and extending westwards to Penrith. The distinctive shape of the Prospect Reservoir lies approximately in the centre of the image. Unfortunately, much of the expansion of Sydney to the south is not represented in these images.
The history of European Australians began in Sydney. Viewed from space, the city is focussed on Sydney Cove but the expansion patterns we can see today are asymmetric around this focus.
The heart of Sydney is the CBD and the density of high-rise buildings and roads appear blue in the 1972 and 1989 FCC image images. The spatial pattern of expansion of urban Sydney is to the south and to the west with less on the Northern shores of Sydney Harbour. The constraints to urban expansion provided by topography, and less so by water, show very clearly in the Northern half of the city. Here the urban spread has been restricted to the valley floors, with the upland areas left with their cover of eucalypt open forests (eM3L AUSLIG, 1990) on rocky sandstone soils. The result is an extraordinary spatial pattern of interlocking fingers: the dark red of the eucalypt forests mingling with the lighter pink-blue urban landcover. There are similar patterns in the south around the Georges River and Port Hacking.
The spectral and spatial patterns of by far the largest part of the Sydney suburban area are characterised not by the underlying landscape but by the built environment. These spatial patterns have a geometry that is shaped by roads almost as far west as the Nepean River. The spectral patterns show an interpretable gradient: beginning with the blues of the dense built-environment of the CBD and parts of Parramatta and Blacktown, it grades through the blue-pink of suburbia where the cover of vegetation (gardens, parks and ovals) is greatest, to the much less densely settled periphery that begins at Liverpool, Mount Druitt and Penrith. Here agricultural landcover (pastures and so forth) dominates the spectral signature, but it is obvious after close examination of the intensity and scale of the spatial patterns that there is a strong influence of Urbanisation.
During the last twenty years, an additional three quarters of a million people, or twice the entire population of Tasmania, have come to live in the Sydney urban area. What impact has this population growth on the landcover of urban Sydney?
The Difference FCC image clearly shows the areas of conversion of agricultural to urban landcover in dark tones. In the west, along the outer fringes, the geometric shapes of new suburbs are visible. Closer in to the CBD, particularly in the south, the sizes of the blocks of landcover change are smaller but distinctly human made. The shapes of land clearing near Holsworthy are not natural. Throughout the inner city suburbs, particularly the southern ones, small cover changes are flagged as black pixels. Many of these are only a few pixels in size and are difficult to interpret. They represent changes that are possibly related to construction and urban infill. I hope that readers more familiar with Sydney are able to identify and interpret these landcover changes.
The substantial population growth in the Sydney urban area during the last 17 years produced landcover changes that were captured in space images and are detectable to the unaided eye. These landcover changes ranged from very small areas in the inner city to much larger areas on the western edges of the urban area. I expected that the changes would be larger in area; particularly those in the west and the south. Perhaps the reason for fewer than expected sprawling suburbs is an increasing tendency towards higher density living in both the inner and outer suburbs. Even though Sydney is decidedly a Car City, it also has the highest proportion of medium density housing.