1972 - 1988

Melbourne is the second largest city in population size. The population of Victoria has grown from 3 million in 1971 to 4.29 million in 1991, at an average rate of ~ 1% per year. During the same period, the population of the city of Melbourne has increased from 2.503 million to greater than 3.1 million. Melbourne contains approximately 70% of the Victoria's population, but its city-state rank has fallen. At the time of the 1971 census, Melbourne held 72% of the state population and was number two on the city-state rank behind Canberra. By 1989, the proportion of the state population held had fallen to 70% and its rank to four behind Canberra, Adelaide and Perth.

We have satellite images with which we can detect and interpret the changes that have occurred between January 19 1973 and December 14 1988; we can look back 16 years on the city of Melbourne.

What can we interpret of the nature and history of the city of Melbourne with a view from space? If we start with the earliest scene, the first impression is how the city dominates the scene; a scene whose total area is ~20 000 km2. Even so the entire urban area of Melbourne is not captured in this scene. Much of the southerly extension along the eastern edge of the bay is outside the image.

Landsat FCC images of the city of Melbourne: January 19, 1972; December 14, 1988; and the 1972-1988 Difference.

Use your browser to open each image in a new window to compare them.

The urban spread of Melbourne sits asymmetrically at the top of Port Phillip Bay and spreads out north and, particularly, to the east where it reaches the Dandenong Ranges. The spread of the city seems little influenced by topography and it is probable that the growth of its suburbs has always been at the expense of peri-urban agricultural land, horticulture in the east and pastures and crops in the west and north.

We can infer a great deal about Melbourne from the spectral and spatial characteristics of its space images. First the spectral characteristics indicate that the area of high density high-rise buildings, roads and vegetation-free landcover - the blue core of the city - is large relative to the surrounding suburbs. It appears to be considerably larger than the equivalent area of Sydney. This region also contains the high density inner-city housing as well as the light industrial areas. It includes the western inner-city suburbs as well as Fitzroy, Collingwood, Richmond, Prahran and St Kilda.

The island of green vegetation showing crimson red in the image - representing the gardens, parks and recreation areas at the beginning of St Kilda Road, Albert Park and South Melbourne - is quite obvious.

In contrast to the blue coloured inner suburban areas of the eastern and western edges of the CBD are the surrounding newer areas of urban expansion. These areas are progressively more crimson in colour, indicating an increasing proportion of green vegetation. In 1973, when most of the surrounding agricultural land was dry, the suburbs of Melbourne were relatively green. Yet the patterns and locations of this suburban greenness differ.

For those readers who know Melbourne, an interesting exercise is to correlate the greenness of a particular residential area as it appears on the image with its average real estate value. Having established that there is a positive correlation, ie the higher the greenness score the higher the real estate value, it is then a puzzle to determine which is cause and which is effect.

The spatial patterning of the Melbourne urban area is also best appreciated in the dry 1973 image. The regular grids of roads and the arterial highways radiating out to the west, north and east are the framework around which the urban pattern has been stretched. Melbourne has been very much the transport focus of economic activity in Victoria, and this pattern of convergence is more obvious from space than in any other capital cities.

By 1973 Melbourne was a Car City with high car ownership levels, low density housing predominating and a very high investment in roads. This pattern continues today.

A comparison of the 1988 image is difficult because the eyes are distracted by the increase in the general level of greenness (crimson colour) across the whole scene. Obviously the rainfall history of December 1988 was considerably more favourable than in January 1973, a time of very severe drought. This increase in greenness also enhances the contrast between the inner, older suburbs that contain very little green landcover and the outer, younger suburbs that contain a great deal more per pixel. The increase in general greenness level tends to subdue the spatial patterning as roads, with vegetated median strips or edges, are less strongly contrasted with the adjacent residential landcover.

What changes in landcover can be detected using the Difference FCC image?

The most obvious features in this image are two very large white objects; one in the Dandenong Ranges and the other further north. Their shape and colour in the 1988 image reveal that they are newly filled water storages, Cardinia Creek and Winneke reservoirs.

What is the pattern of dark tones? This spectral signature indicates the change of agricultural (vegetation) to urban landcover at sometime between the two dates. The general impression is that there are no large blocks of land that have been converted to suburbs either within the established residential area or around its periphery. The pattern of change is many small areas diffused amongst the urban area generally. The largest areas are near Altona and there are clusters of urban change in the upper Yarra Valley and in the Dandenong Ranges. The urban fringe in the north grades into agricultural landcover and many small changes found here may be routine agricultural rather than urban expansion and transformation.

In summary

The landcover changes that we can detect during the last 16 years of growth of the Melbourne urban area are small and diffuse. This is in contrast to Sydney where urban expansion was concentrated in its western suburbs. From space Melbourne has all the characteristics of a Car City: it is a sprawling, low density city whose spatial pattern is shaped by a grid of roads. Though exact visual assessment is difficult, the size of the urban area of Melbourne appears greater than that of Sydney, even though the latter has the larger population and Melbourne appears to have a larger high-density inner city core.