Is WSUD implementation really worth it?: Using ecosystem service values to determine the cost benefit of improved stormwater management

Across Australia, jurisdictions are faced with pressure between development and an ongoing environmental duty of care. Nowhere is this more apparent than in the case of the management of stormwater and water quality impacts in receiving environments. While the costs of implementing and maintaining stormwater infrastructure (whether it be 'on-site' or 'off-site') is reasonably well understood, the economic implications of the environmental trade-offs involved in potential stormwater management strategies are less apparent. In a recent study considering the cost-benefit of a range of scenarios for improved stormwater management in future development within the Lake Illawarra region, ecosystem service valuation techniques were used to derive the value of achieving a range of water quality targets. Ecosystem services range from provisioning services (of food, fibre, energy etc.), regulating services such as climate and hazard management and cultural services like education and tourism. Determining their value depends on identifying whether those services have value in a market, and whether the services will be affected by the scenarios being considered, such as future urban development. In this study, it was found that certain services such as food provisioning through fisheries could be impacted by deteriorating water quality and this was quantified through numeric modelling. Improvements in water quality through implementing WSUD practices in future development could also be quantified and therefore the benefits of such strategies (as avoided costs or prevention of the loss of value of relevant ecosystem services) could be determined. This showed that based on the value of the commercial and recreational fisheries within Lake Illawarra alone, implementation of WSUD to meet several water quality targets was cost-beneficial, though this may be difficult to demonstrate for some parameters where a causal link between the parameter and a change in ecosystem service value could not be easily quantified.