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Typically designed to handle the smaller, most frequent storm events, LID practices in Southern Ontario are usually sized according to the [[Runoff_volume_control_target| 90th percentile event]]. In many areas this translates into events that are <30 mm in size. Note that 25 mm is considered to be a suitable representation of the ‘first flush’ volume, and that controlling this amount of runoff provides stormwater engineers with control over 90% of the mean annual pollutant load <ref>Pitt, R. 1999. Small Storm Hydrology and Why it is Important for the Design of Stormwater Control Practices. In: Advances in Modeling the Management of Stormwater Impacts, Volume 7. Computational Hydraulics International, Guelph, Ontario and Lewis Publishers/CRC Press. 1999</ref>.
→Alleviating pressures using LID
A central tenet underpinning low impact development approaches to stormwater management is the [[treatment train]] approach, which describes a hierarchical suite of practices which manage rainfall where it falls, followed by the attenuation, filtration and infiltration of stormwater along its path of travel and – eventually – using an end-of-pipe detention and polishing process. While many LID practices – including [[bioretention]], soakaway pits and others – are not necessarily intended to remedy issues related to urban flooding per se, they are effective at easing the pressure on aging, overburdened stormwater infrastructure. That being said, there are new options in the LID toolkit which have the capacity to provide both peak flow and large event runoff volume control.
A central tenet underpinning low impact development approaches to stormwater management is the [[treatment train]] approach, which describes a hierarchical suite of practices which manage rainfall where it falls, followed by the attenuation, filtration and infiltration of stormwater along its path of travel and – eventually – using an end-of-pipe detention and polishing process. While many LID practices – including [[bioretention]], soakaway pits and others – are not necessarily intended to remedy issues related to urban flooding per se, they are effective at easing the pressure on aging, overburdened stormwater infrastructure. That being said, there are new options in the LID toolkit which have the capacity to provide both peak flow and large event runoff volume control.
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[[category:Planning]]
[[category:Planning]]