Analyses of the hydrologic performance of bioretention facilities

Seyed Amirali Alinaghian and James Li


Due to urbanization, and replacing natural pervious lands by impermeable surfaces, the patterns of rainfall-runoff are altered and thus, negatively influence natural water systems regarding both water quantity and water quality. These impermeable surfaces (e.g., roofs, roads, parking lots, …) prevent rainfall from infiltration into soil structure, which results in water quantity issues such as increased runoff volumes, and high peak flows.

Recently, Low impact development (LID) technologies are receiving increased attention for the management of stormwater runoff from developed sites. LID strategy is a popular technique that emphasizes at on-site stormwater management in developed and developing areas with the aim of imitating the hydrologic features of pre-development situations. Bioretention as an efficient LID practice has received significant interest in the recent years.

Bioretention practice due to its advantages can be considered as one of the most promising LID practices that maintain the fundamental hydrologic functions in a natural environment and can be integrated into neighborhood landscaping.

The primary objective of the current study is analyzing the effects of inflow and outflow characteristics on right-of-way (roadside) bioretention facilities. In order to attain this goal, we try to focus on the inlet and outlet flow hydrographs under several design storm conditions. After the formulation of a SWMM model (node and link plus LID), numerical experiments including sensitivity analysis will be designed to simulate and investigate the runoff control performance of a right-of-way bioretention facility. As a case study, we have used the City of Toronto project (Queensway Sustainable Sidewalk Study: Stormwater Performance Evaluation of sustainable sidewalks in the City of Toronto). The City of Toronto has used a 10 inches perforated pipe for distributing the water over the Bioretention cell (Silva cell). For the movement of water inside the perforated pipe, we have developed a CFD model with the help of FLOW 3D software. The last step is to synthesize the numerical experimental results into recommendations for the better design of the bioretention facility.

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