Changes

[[File:90th percentile.png|thumb|Recommended regional 90th percentile volume targets for Ontario]]

[[File:90th percentile.png|thumb|Recommended regional 90th percentile volume targets for Ontario]]

Typically designed to handle the smaller, most frequent storm events, LID practices in Ontario are usually sized according to the 90th percentile event. In many areas this translates into events that are < 30 mm in depth. Note that 25 mm is considered to be a suitable representation of the ‘first flush’ volume, and that controlling this amount of runoff may provide 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>.

Typically designed to handle the smaller, most frequent storm events, LID practices in Ontario are usually sized according to the 90th percentile event. In many areas this translates into events that are < 30 mm in depth. Note that 25 mm is considered to be a suitable representation of the ‘first flush’ volume, and that controlling this amount of runoff may provide 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>.