1972 - 1988
Brisbane is a large and sprawling city with the lowest proportion of its population (8%) living in medium or high density dwellings. Sydney, by comparison, has 21% of its population in medium to high density dwellings.
The Landsat images we have to look back at the changes were acquired on November 11, 1972 and sixteen years later on November 16, 1988. The cities of Brisbane and Ipswich are clearly visible along the diagonal axis of the image. We will include Ipswich and surrounds as part of the Brisbane urban area.
The 1991 first count population of the Brisbane Statistical Division was 2 978 617 and Brisbane has been growing at a rate of ~ 2% per year. Queensland has the highest population growth rate of all states (~ 3%) and its population will exceed that of Victoria within the next few years. Interestingly, Queensland is a very decentralised state because Brisbane has only 45% of the state population. The larger coastal cities and country towns contain much of the remaining population.
The historical development of Brisbane can be interpreted using the view from space. The location of the CBD is inland from the mouth of the Brisbane River. The urban area is rather symmetrically focussed on the CBD; spreading outwards in concentric fronts constrained in the north by the D'Aguilar Range and in the south by its subdued continuation. The outgrowths of Urbanisation follow the major transport corridors to the west, north, and south. Brisbane has grown to be a sprawling Car City.
Three Landsat FCC images of the city of Brisbane: December 11, 1972; November 11, 1988 and the 1972-1988 Difference.
Use your browser to open each image in a new window to compare them.
Within this Brisbane scene there is agricultural landcover (pastures and crops), plantation forestry, and Urbanisation. The only extensive natural landcover remaining is the eucalypt open forest (eM3L, AUSLIG 1990) on the steep uplands. The distinctly human-made infrastructure of roads and powerlines adds sharp linear contrasts to the varied spatial patterns of the natural landscape beneath.
An eyeball comparison of the 1972 and 1988 FCC images shows that there were very different seasonal conditions at the two acquisition dates.
In 1972 most of the landcover other than urban was very dry and non-green. The agricultural areas show a gun-metal blue signature characteristic of dry grass, and only the eucalypt woodlands show the red colour that indicates green leaves. Very few suburbs show much red colour. My interpretation of this is that it indicates the extent to which the condition of the home gardens and street vegetation is dependent on rain rather than artificial watering. The summer rains had obviously not begun in November 1972 and the conditions of Brisbane suburbs are in contrast to those of Melbourne.
The seasonal conditions obvious in the November 1988 FCC image were very different from those 16 years previous. Almost all the agricultural landcover has greened up in response to rain. By looking at this FCC image and comparing it with the 1972 image, you can get a good feel for vegetation types. The largely undisturbed eucalypt woodlands have the most distinct and invariant signature. If you follow the gradations away from these uplands down to the lowlands you can distinguish various levels of clearing, of grassland types and of hobby farms.
It is curious that even when the rural surrounds of Brisbane are green, most of the inner city suburbs show little or no vegetation response. I suspect that like Melbourne there is a strong correlation between real estate value and the level of greenness observed in space images. Those readers who have a better understanding of Brisbane will no doubt be able to interpret far more of these FCC images than I can.
In the Difference FCC image, the seasonal changes have largely been suppressed because changes in landcover condition are not our principal concern. In this Chapter, we are interested in the irreversible changes in landcover type; from non-urban to urban. As for the other cities we can begin to detect the landcover change by spectral characteristics and its nature by interpreting its spatial patterns.
The colour changes that immediately take the eye are the white shapes of the water bodies. The most striking human-made change between 1972 and 1988 is the establishment and filling of at least 3 large water storages: a very large one in the west; the Pine River Dam in the north; and the smaller Lake Manchester, west of centre. These appear white in the Difference FCC image. Because white indicates a darkening in 1988 compared with 1972, we can see and interpret the tidal changes in the Logan River, in an inlet near Cribb Island as well as along the beach front at Redcliffe and Mud Island.
There is a scattering of small areas of landcover with a crimson spectral signature indicating a sharp change (decline) in greenness between the two dates. The spatial patterns of these areas suggest small agricultural fields and confirm our interpretation.
The landcover change that we are particularly interested in is flagged by the dark patches that indicate a change from dark vegetation in 1972 to brighter bare soil or newly created urban areas in 1988. The pattern is as might be expected. It is most common on the periphery of the existing Urbanisation and close to existing transport corridors. In the north it is next to the Gympie Road and in the south, the freeway section of the Pacific Highway. These changes in the upper reaches of the Logan River appear by the spatial patterning to be urban rather than rural related landcover change. I think we can reasonably interpret these to be the establishment of hobby farms.
One small change I noticed, because much of my experience of Brisbane is from the air, was the landcover changes associated with the new Brisbane airport. If you search for these, you will find that the airport complex has been located on a coastal plain and that the central runway replaced a mangrove-lined wetland.
Wetlands are vitally important nursery areas for various marine species, many of which we harvest and enjoy. This small example helps to explain why I see a steadily increasing number of recreational fishing boats in Moreton Bay pursuing an ever-decreasing catch of fish and crabs.