Effectiveness of Water-Sensitive Urban Design Techniques on Stormwater Quantity Management at a Residential Allotment Scale

Rapid population growth and urbanization are transforming natural landscapes into built environments, resulting in increased stormwater runoff, which poses significant challenges for local governments to manage. Water-Sensitive Urban Design (WSUD) techniques have been implemented to enhance urban stormwater quality, but their effectiveness in managing stormwater quantity and quality across different scales remains uncertain. This study examines the capacity of various WSUD approaches to reduce stormwater runoff volume and peak flow rates in a residential allotment transitioning from a single dwelling to a redeveloped condition with two dwellings. The tested techniques included a rainwater tank, infiltration trench, rain garden, vegetated swale, and permeable pavement. For storm events with a 1-in-5-year Annual Recurrence Interval (ARI)—aligning with typical piped drainage design standards—peak flow rates were reduced by 90% in the redeveloped scenario. Smaller storm events, up to a 1-in-1-year ARI, were frequently eliminated, thereby minimizing disturbances to waterways caused by frequent runoff discharges. Among the tested techniques, the combination of a rainwater tank, rain garden, and infiltration trench demonstrated the greatest effectiveness in reducing stormwater runoff volume and peak flow rates despite considerations of life cycle costs. These findings highlight the potential of integrated WSUD techniques in addressing urban stormwater management challenges.