Techno-Economic Evaluation of Vegetated Swales for Urban Stormwater Management in South Australia

ABSTRACT: Urban stormwater runoff continues to challenge cities worldwide due to increasing impervious surfaces and intensified rainfall from climate change. Swales—vegetated conveyance channels designed to manage runoff volume and quality—offer a nature-based solution that integrates hydrological function, ecological enhancement, and cost-effectiveness. This study investigates the performance and lifecycle economics of swale systems using a case study in South Australia. A MUSICX model simulation was conducted to quantify pollutant removal and flow reduction, and lifecycle costing was performed to evaluate construction and annual maintenance requirements. Results indicate exceptionally high treatment efficiencies, with over 99% removal of total suspended solids, nitrogen, phosphorus, and gross pollutants, and a 99.09% reduction in runoff volume. The total capital cost of the swale network was estimated at $19,726.50, with annual maintenance at $6157.49. Economic benefits from pollutant removal and avoided downstream treatment were valued at $14,874 per year, demonstrating a favorable benefit-cost profile. The findings underscore the potential of well-designed swales to function as cost-effective, modular components of decentralized stormwater management systems. These results contribute evidence supporting the broader integration of swales into urban planning, particularly in water-sensitive design frameworks seeking to achieve sustainability, climate adaptation, and SDG-aligned outcomes.