Modelling for Integrated Stormwater Management of the Renfrew Neighbourhood: A Pilot Study

The Renfrew Neighbourhood within the City of Calgary is about 1.3 km² and is undergoing infill redevelopment with effective lot imperviousness increasing three-fold, straining the existing storm sewer system. Combined with existing localized flooding, the City of Calgary is challenged with providing adequate flood storage and improving downstream water quality. These challenges are not unique to the Renfrew Neighbourhood, but permit the project and location to be used as a pilot study to compare the cost effectiveness of different retrofit options using a novel benefit optimization approach. Four potential retrofit options were identified for integrated stormwater management: pipe replacement (size) inlet flow controls, distributed management (LID/SUDS/WSUDS), regional or community storage, and a combination of controls. Hydrologic and hydraulic analyses conducted using EPA SWMM was coupled with an extension software package (Optimizer^TM) to determine the placement and sizing of improvements for each scenario that most cost-effectively managed runoff for future redevelopment conditions. Optimization can often result in significant cost savings over more traditional infrastructure planning approaches. By using optimization software, planning can minimise costs and maximize flood control and water quality benefits. Runoff conditions from small storm events through a 50-yr, 4-hr design event for the 2076 redevelopment conditions were considered in scenario optimization. Results from the analyses demonstrate the value of using an optimization approach for long-term integrated stormwater planning which can serve as a template for future capital improvements.