Changes

===Stream Channel Erosion===

===Stream Channel Erosion===

The feasibility of storing the channel erosion control volume within bioretention areas will be dependent on the size of the drainage area and available space. It may prove infeasible due to the large footprint needed to maintain the recommended maximum ponding depth of 200 mm. Meeting the channel erosion control requirement through bioretention is most feasible in the regions of the Greater Toronto Area with [[Soil groups|A and B soils]]. In these situations, the reduction in runoff volume through infiltration and evapotranspiration may be sufficient. It is important to note that the bioretention practice will infiltrate runoff throughout the course of the storm; so the actual capacity of the bioretention cell to capture runoff from the drainage area will be larger than its designed storage volume.

The feasibility of storing the channel erosion control volume within bioretention areas will be dependent on the size of the drainage area and available space. Meeting the channel erosion control requirement through bioretention is most feasible in the regions of the Greater Toronto Area with [[Soil groups|Hydrologic Soil Group A and B soils]]. In these situations, the reduction in runoff volume through infiltration and evapotranspiration may be sufficient. For facilities with constrained footprints, include a flow restrictor on the underdrain perforated pipe or outlet storm sewer to control the release rate, and size the internal water storage reservoir to retain the necessary volume of water. Where acceptable, consider increasing the maximum ponding depth beyond the recommended 350 mm. It is important to note that the bioretention practice will infiltrate runoff into the filter media bed and underlying native soil over the duration of the design storm event, which can be factored into surface ponding and internal water storage reservoir sizing to optimize the design. See [[Bioretention: Sizing | Sizing]] for further guidance.

===Other Benefits===

===Other Benefits===