Case Study: Using What-If? to guide appropriate infill development

Outline of the Research

As our major cities continue to grow, potential tensions between the need to provide land for urban development, and protect sensitive ecosystems on the urban urban fringe are likely to arise. This project, undertaken by Dr. Georgia Garrard, Dr. Kath Phelan, Dr. Sarah Bekessy, Dr Simon Van Wijnen, Dr. Joe Hurley, and Professor Michael Buxton at the Centre for Urban Research at RMIT, aimed to model the spatial development of Melbourne based on Victorian Government population, housing and jobs projections to 2031.

The project assumed that 50% of new dwellings would be accommodated in new sustainable mid-rise development in existing and growth areas of Melbourne and that no new low density residential development would be added to existing stock. Using previous work on residential land supplies, the project assumed that 80% of new dwellings would occur in already developed areas of Melbourne. This differs to current planning policy for growth areas which Plan Melbourne (2014) anticipates will accommodate 40% of new residents. The project used previously identified areas for infill development within Melbourne. The project allocated new land uses according to Victoria’s Planning Scheme, proximity to public transport and activity centres, and heritage and environmental planning overlays. The project prioritised development away from areas that contained native grasslands and other threatened or vulnerable ecological communities.

How AURIN was used

The researchers used Online WhatIf? to underpin their scenario modelling. Online WhatIf? is a GIS-based online, open source planning support system developed as part of the AURIN workbench. It can be used to support important aspects of land planning, including: analyzing the suitability of land for different uses; projecting future land use demands; and allocating the projected demands to the most suitable locations. The researchers used online WhatIf? to demonstrate the implications of alternative development approaches for Melbourne. At the metropolitan scale, the researchers used AURIN’s Online WhatIf? to assess the impact of this type of development on native grasslands, and accessibility to public transport over a range of time periods into the future, to 2031. The researchers were able to incorporate different demand scenarios into their model, with different amounts of infill and greenfield development, to model the impact of different development types on land use at the urban fringe

Illustration of the locations of new development between 2016 and 2031 under the “Infill 80” scenario, modelled using AURIN’s Online WhatIf?

Impact of the research

The researchers were able to show that a development scenario where 80% or 60% of new dwellings are infill (rather than greenfield) reduced low density and very low density development in ecologically sensitive areas. This occurred in two ways; firstly, by reducing the number of new dwellings in growth areas (20% of all new houses compared to 40% as is currently proposed); and secondly, by increasing the density of new dwellings in the growth areas. By both increasing infill development in existing areas, and producing higher density dwellings in new areas, it may be possible to substantially reduce pressure on sensitive and unique ecosystems on Melbourne’s doorstep