Spatial analysis of residential urban form changes: a detailed-geography approach to monitoring results of urban consolidation policy, exemplified for the Melbourne Metropolitan Area

The study results reported here refer to devising improved ways of monitoring the considerable urban residential form changes that have resulted from implementation of the Victorian urban consolidation policy during the intercensal period 2001-2006. The policy applies to the Melbourne Metropolitan Area (MMA) and was designed (among other things) to de-emphasise urban sprawl while facilitating the construction of new dwellings during a time of rapid population growth. Thus, accommodation has involved not only greenfield land development but also population densification via brownfield and infill (re)development in Local Government Areas (LGAs) that were first populated during earlier city expansion phases when the extent of the metropolitan area was smaller than today. The policy is designed to improve the return on investment in existing infrastructure and services, as well as housing affordability and residential liveability. Most of the infill has taken place in the suburbs that were zoned/designated greenfield sites four to five decades ago. Here, both strategic (redevelopment around designated activity centres and around principal public transport networks) and dispersed “infill” development have been facilitated in policy implementation. Most of the “infill” is in the form of backyard developments/land-parcel-sub-division or replacement of old housing to make room for two or more new dwellings. The pattern of change due to this indicates that it has evolved as opportunity presented itself in a booming MMA land and property market. This “retro-fit” of extra dwellings is such that the capacity of some extant infrastructural (e.g. the storm water pipe network) and social service (e.g. schools and clinics) assets may be exceeded while that of others (e.g. the transport network) is likely to become better exploited. In contrast, the liveability and social sustainability of dwellers in newly-developed greenfields is dominated by the lack of access to the public transport network and further distance to public services (i.e. schools and public hospitals). A high level of automobile dependence is imposed on them by the persistence of the traditional urban sprawl approach to land-use planning, even though semi-detached houses and apartments have become included in the dwelling stock, thereby mitigating this tendency somewhat. In all cases of residential urban form change, the social, institutional and environmental impacts spawn a need for site selection for implementation of targeted mitigation measures. The pre-requisite for this task is detailed residential urban form mapping and monitoring. However, at policy launch, and even after eight years of implementation, the traditional approach to urban growth analysis using spatially-aggregated data had not been complemented by the detailed geographies that would serve the necessary monitoring. Thus geographical variation in the pattern of urban form change across a metropolitan area accommodating nearly four million people and governed by thirty one local government areas (LGAs) is undocumented in terms of the pattern of relative significance of greenfield, brownfield and infill development. Accordingly, both statutory and strategic decision support systems lack data and information that would serve them well. The lack of adoption of the full power of digital spatial data handling implied by this, is despite the fact that the various Australian state geographical data coordination committees charged with promoting the analogue-to-digital conversion of public sector mapping were established nearly two decades ago. By way of mitigation, the study reported here is designed to develop a Geographical Information Systems (GIS) parcel-based method for identifying and mapping the extent and location of infill development using various spatial datasets acquired and accessible from local and state government departments. Thus has emerged a method for detailed mapping of not only the pattern changes in the infill development pattern, LGA by LGA, but also the pattern of social impacts, identifiable in terms of census geography. Project results (e.g. as summarised in thematic maps) show that the success of Melbourne 2030 implementation varies across the MMA. For the study period, the trend was that LGAs offering room for new dwellings by brownfield and infill re-development did not see Activity Centres favoured by infill developers. Accordingly, such data integration and analysis as exemplified by this study will be useful in both strategic and social planning, because in both cases, it is important to monitor the actual outcomes for comparison with policy goals. In addition, those involved in site selection and prioritising for the provision of new or up-graded infrastructure, facilities and amenity can be better informed and, thereby, more effective. It is shown that the data streams currently accessible to LGA planning departments in the cities dominated by residential areas established four or five decades ago support the application of spatial statistics and modelling in ways that would allow the relative significance of driving forces and of densification impacts to be derived if the necessary data sharing arrangement can be established. Indications from the present study are that dwelling renewals within a 600 to 800 meter zone buffering the railway stations, or 400 meters of activity hubs like Colleges/University, define most of the infill developments, and that this is more marked if the re-developed housing stock is old enough to have been part of the traditional post WWII quarter acre block greenfield developments. Clearly, those interested in predicting future (opportunistic) infill pattern change trends will be planning spatial queries dominated by interest in documenting the condition (including age) of housing stock in the vicinity of transport network nodes. Adoption for decision support up-grade for further implementation of Melbourne 2030 may be inspired by this study. However, it requires that the stakeholder representatives (e.g. LGAs, community associations, and state government authorities) can agree to sharing the necessary data maintenance and processing costs. It is argued that there is no longer any reason for the detailed geographies exemplified here to be ignored in urban residential form change monitoring in Melbourne, or any other metropolitan area faced with accommodating population growth while maintaining livability without unmitigated urban sprawl with its continuous call for infrastructure subsidy.