Does Water Sensitive Design Deliver Beneficial Net Economic Outcomes?

Councils across New Zealand face a number of significant stormwater problems arising from the growth, development and redevelopment of urban centres. Water sensitive design (WSD) has been offered up as a solution to addressing the effects of stormwater discharges. However, a key impediment to its implementation is the perception that WSD costs more than conventional stormwater management approaches in both implementation and operation. Previous papers by the authors have described the life cycle costing model used to estimate costs associated with different urban development scenarios within a decision support system (DSS) called “Urban Planning that Sustains Waterbodies” (UPSW). UPSW is a catchment-scale spatial tool that discriminates between catchment development scenarios in terms of their impacts on receiving waterbodies. The outcomes of each scenario are portrayed through a set of indicators that reflect their influence on the environmental, social, economic, and cultural wellbeings associated with the receiving waterbodies. This paper describes refinements made to the life cycle costing model that allow users to compare the costs and benefits of conventional and WSD stormwater management for future catchment development scenarios. In this way users can determine whether beneficial net economic outcomes can be obtained from WSD stormwater management. The refinements integrate ‘real world’ costing data with findings from an international literature review which investigated cost comparisons between WSD and conventional stormwater management.