An evaluation of applying existing bioretention sizing methods to cold climates with snow storage conditions

A Comprehensive Review of Low Impact Development Models for Research, Conceptual, Preliminary and Detailed Design Applications

This review compares and evaluates eleven Low Impact Development (LID) models on the basis of: (i) general model features including the model application, the temporal resolution, the spatial data visualization, the method of placing LID within catchments; (ii) hydrological modelling aspects including: the type of inbuilt LIDs, water balance model, runoff generation and infiltration; and (iii) hydraulic modelling methods with a focus on the flow routing method. Results show that despite the recent updates of existing LID models, several important features are still missing and need improvement. These features include the ability to model: multi-layer subsurface media, tree canopy and processes associated with vegetation, different spatial scales, snowmelt and runoff calculations. This review provides in-depth insight into existing LID models from a hydrological and hydraulic point of view, which will facilitate in selecting the best-suited model. Recommendations on further studies and LID model development are also presented.

Modelling hydrology of a single bioretention system with HYDRUS-1D

A study was carried out on the effectiveness of bioretention systems to abate stormwater using computer simulation. The hydrologic performance was simulated for two bioretention cells using HYDRUS-1D, and the simulation results were verified by field data of nearly four years. Using the validated model, the optimization of design parameters of rainfall return period, filter media depth and type, and surface area was discussed. And the annual hydrologic performance of bioretention systems was further analyzed under the optimized parameters. The study reveals that bioretention systems with underdrains and impervious boundaries do have some detention capability, while their total water retention capability is extremely limited. Better detention capability is noted for smaller rainfall events, deeper filter media, and design storms with a return period smaller than 2 years, and a cost-effective filter media depth is recommended in bioretention design. Better hydrologic effectiveness is achieved with a higher hydraulic conductivity and ratio of the bioretention surface area to the catchment area, and filter media whose conductivity is between the conductivity of loamy sand and sandy loam, and a surface area of 10% of the catchment area is recommended. In the long-term simulation, both infiltration volume and evapotranspiration are critical for the total rainfall treatment in bioretention systems.

Removal and fate of polycyclic aromatic hydrocarbon pollutants in an urban stormwater bioretention facility

This research investigated the removal and fate of 16 USEPA priority pollutant polycyclic aromatic hydrocarbons (PAHs) from urban stormwater runoff through a bioretention cell. Bioretention is an infiltration/filtration practice containing a mixed layer of about 90 cm of soil, sand, and organic matter, planted with appropriate vegetation. Field water quality monitoring and bioretention media core analyses were performed. The results indicate that bioretention is a promising management practice to control runoff PAH pollutants. The PAH event mean concentration (EMC) reduction ranged from 31 to 99%, with a mean discharge EMC of 0.22 microg/L. The mass load decreased from a mean value of 0.0180 kg/ha yr to 0.0025 kg/ha yr, suggesting an average PAH mass load reduction of 87% to the discharging watershed. The most dominant PAH species monitored were fluoranthene and pyrene. Influent PAHs indicated strong affiliation with runoff total suspended solids (TSS). As such, PAH removal positively correlated with TSS removal. Low rainfall depth was associated with high influent PAH concentration and resulted in favorable PAH removal. Source investigation suggested that the PAHs measured in the monitored cell were from pyrogenic sources, likely resulting from vehicle combustion processes. Sealers used in parking lots and driveway coatings were also a possible source of PAHs. Media core analyses indicated that the intercepted PAH compounds transported only a few centimeters vertically in the soil media near the runoff entrance location, suggesting that a shallow cell design may be adequate for systems focusing on PAH removal.