Furthermore, with the rise in urban development and subsequent expansion of impervious areas, stormwater runoff volume has increased, leading to more frequent combined sewer overflows (CSOs) and conveyance system surcharge ( Stovin et al. It was established that one of the largest contributors to nonpoint source pollution of estuaries and lakes is the urban runoff generated by regularly occurring storm events which make up 90% of storms in a year ( USEPA 1983). However, concerns emerged about the influence of continual runoff and pollutant loading of downstream water bodies. Traditional stormwater management methods drain runoff as quickly and efficiently as possible ( MDDEFP 2014).
The evaluated LID Control module presented better predictive capabilities for the basin with a simpler overall design (VS). 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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