An infrastructure potential cost model for integrated land use and infrastructure planning

Abstract

The purpose of the bulk infrastructure potential cost model is to provide a tool for planners to ensure the incorporation of bulk infrastructure cost considerations into the early, land suitability assessment phase of the integrated development planning process. In practice, infrastructure planning has generally tended to follow land use planning with infrastructure costs seeming to play no role in the generation of land use strategies. The output of the model is in the form of potential cost maps which facilitates the relative comparison of infrastructure costs for different density scenarios. Bulk engineering services infrastructure relating to water, sanitation and electricity have been included in the model. The theoretical underpinning of the model is threshold analysis. There are three essential elements of the bulk infrastructure cost model: threshold, density and cost. The manner in which the three pillars are incorporated into the model is through capacity analysis. The density levels set, convert into the number of additional person units required, which in turn translate into infrastructure capacity demand. Existing infrastructure network and facility design capacities are compared with current utilisation of infrastructure in order to quantify the capacity supply situation. The comparison of capacity demand with capacity supply determines whether or not additional infrastructure is required. If infrastructure is required, the required infrastructure investment is calculated. The resulting relative costs are mapped and incorporated into a wider land suitability assessment model to identify suitable land for low income residential development. The models are contextualised as Spatial Planning Support Systems, supporting a specific planning problem, with a strong spatial component, incorporating a multicriteria evaluation and cost model and being loosely-coupled with GIS. It is shown that although bulk infrastructure potential costs can be incorporated into the land suitability assessment process to enhance the land delivery decision making process, it is preferable to keep the cost analysis separate from the analysis of the more "softer" issues. Conclusion are made in relation to a number of key developmental issues: the sprawl/densification debate, land and housing policy issues, sustainability, integration, affordability and bulk services contribution rates.