Urban streams are degraded by conventional stormwater drainage systems, typically causing substantial hydraulic, physical form and chemical disturbances. This world-first, long-term, multi-disciplinary project tested whether dispersing Stormwater Control Measures (SCMs) across a catchment can restore stream ecosystem structure and function by mimicking pre-urban hydrology.
The Little Stringybark and Dobsons Creeks Projects involved constructing almost 1,000 SCMs on public and private land, designed for harvesting, infiltration, and evapotranspiration. A Before-After-Control-Reference-Impact (BACRI) study framework was used, with continuous monitoring of stream hydrology and intermittent monitoring of water quality and ecological indicators.
Key findings provide proof-of-concept for stream restoration. Hydrology improved, with SCMs reducing wet weather flows for small-to-moderate rainfall events (2-8 mm). In sites with high stormwater retention, peak flows approached reference conditions for rainfall events up to ~12 mm. Phosphorus concentrations and summer temperatures were similar to reference levels during dry weather and after small rain events. Preliminary ecological outcomes varied; Little Stringybark Creek showed little overall change, while Dobsons Creek exhibited a positive trend in macroinvertebrate assemblage composition.
The results of this project provide evidence supporting the adoption of flow-based stormwater objectives, such as those outlined in EPA Victoria’s 2021 Urban Stormwater Management Guidance. Achieving these objectives requires implementing SCMs that manage both quality and quantity of runoff from almost all impervious surfaces. Successful implementation must be integrated across multiple-scales, from private properties to end-of-pipe systems. To ensure long-term environmental benefits, strategies should consider incentives and regulations, enhanced maintenance education, and potentially incorporate real-time monitoring technologies.