The bioretention basin calibration did not prove as successful. Both the alteration of the LID structure representation and the parametric calibration greatly improved the simulated outflows from the vegetated swale resulting in an increase of the Nash–Sutcliffe efficiency (NSE) coefficient from −0.6 to 0.64 (NSE >0.5 is acceptable for hydrologic models according to the literature). In addition, a sensitivity analysis was completed, and the most influential parameters were identified as the conductivity slope and seepage rate. However, it was necessary to change their model representation to account for the non-rectangular shape of the soil layer. Initially, the modeled LID structures were sized identically to the field surface areas. Two types of LID facility were modeled: one releases captured inflow through a perforated underdrain below the soil layer (bioretention basin BB) and the other is drained at the surface of the soil layer (vegetated swale VS). Data collected in 2019 from the monitoring of a pilot project in Montreal was used to verify the ability of the Bioretention LID Control (which assumes a rectangular cross-section) to accurately simulate outflow from a structure with a trapezoidal cross-section. The Low Impact Development (LID) Control module is utilized in the United States Environmental Protection Agency’s Stormwater Management Model (USEPA SWMM) to predict the hydraulic performance of a variety of sustainable stormwater technologies.
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