Bioretention: Streetscapes
Contents
Hydraulically separated or connected with an underdrain, these are often quite small units of 5 - 50 m2 each. In urban settings the bioretentionA shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation. may be bounded entirely with hardscape, restricting options for pretreatment and sheet flow. Amenity and safety can be enhanced on sidewalks with a short (~ 45 cm wall) for seating, although the finished grade is usually only slightly lower than surroundings. Where underground space permits, shade trees are common feature of these facilities, enhancing the streetscape experience and optimizing transpiration. This type of bioretentionA shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation. is often designed offlineRefers to a system that when full, stormwater will bypass the practice. Offline systems use flow splitters or bypass channels that only allow the water quality volume to enter the facility. This may be achieved with a pipe, weir, or curb opening sized for the target flow, but in conjunction, create a bypass channel so that higher flows do not pass over the surface of the filter bed., with bypass overflow.
An excellent opportunity for integrating more bioretentionA shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation. into the street is through careful design of curb extensions for traffic control. See Roadside safety for design advice specific to this application.
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Curb extension in Victoria. Image credit Dylan Passmore
'OfflineRefers to a system that when full, stormwater will bypass the practice. Offline systems use flow splitters or bypass channels that only allow the water quality volume to enter the facility. This may be achieved with a pipe, weir, or curb opening sized for the target flow, but in conjunction, create a bypass channel so that higher flows do not pass over the surface of the filter bed.' streetscape bioretentionA shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation. with trees, King Street, Kitchener
BioretentionA shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation. on residential street, with covered drain inlet (grate in the gutter) and iron grate covered overflow in the centre of the cell, Hinsdale, IL Photo credit: CNT
Curb extension in downtown Indianapolis, IN
Curb extension on Queen Lane, in Philidelphia
Photo credit: PWD
Rainwater harvesting cisternTank used to store rainwater (typically roof runoff) for later use., which discharges to tree pits during dry conditions. Image credit Mississippi WMO
Extended tree pit planting in USA
Photo credit: USEPA
A right of way bioswaleLinear bioretention cell designed to convey, treat and attenuate stormwater runoff. The engineered filter media soil mixture and vegetation slows the runoff water to allow sedimentation, filtration through the root zone, evapotranspiration, and infiltration into the underlying native soil. installed by the New York City Department of Environmental Protection on Dean Street, Brooklyn
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