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| | [[File:Interevent times.PNG|thumb|link=https://public.tableau.com/views/StormIntereventTimesOntario/Dashboard1?:embed=y&:display_count=yes&publish=yes|Darker teal locations have more frequent rainfall; darker yellow have the least frequent rainfall. This image links to a Tableau dashboard, where the interactive data may be viewed in more detail.]] |
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| | The recommended drawdown times for all storage and [[infiltration]] facilities ([[infiltration trenches|trenches]], [[infiltration chambers|chambers]], [[bioretention]] etc.) are based upon rainfall statistics and likelihood that the facility will have had time to regenerate storage capacity before the arrival of the next storm event. |
| | A summary analysis of 14 locations across Ontario found that storms were most frequent in Thunder Bay and least frequent in Toronto; there is a ~50% chance of rainfall occurring again within 48 hours (Thunder Bay) to 72 hours (Toronto). |
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| | The analysis was conducted using the recommended minimum inter-event time of 12 hours from the MOECC<ref>Aquafor Beech, EarthFX. Runoff Volume Control Targets for Ontario Final Report. 2016:125. http://www.downloads.ene.gov.on.ca/envision/env_reg/er/documents/2017/012-9080_Runoff.pdf. Accessed September 11, 2017.</ref>, and earlier rainfall probability distribution parameters from 1960's-1980's <ref>Adams, B. J., and Papa, F. (2000). Urban stormwater management planning with analytical probabilistic models. Wiley.</ref>. |
| | It is not anticipated that recent incremental changes to our climate will have significantly impacted this broad window of recommended drainage times. |
| | Locations considered included: |
| | <div style="column-count:3;-moz-column-count:3;-webkit-column-count:3"> |
| | *Brantford |
| | *Etobicoke |
| | *Hamilton |
| | *Kingston |
| | *London |
| | *Niagara Falls |
| | *Oshawa |
| | *Ottawa |
| | *Peterborough |
| | *Sault Ste Marie |
| | *Thunder Bay |
| | *Toronto |
| | *Trenton |
| | *Windsor |
| | </div> |
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| [[File:Thunder Bay and Toronto.png|thumb|Storm inter-event times for Thunder Bay and Toronto]]
| | ==Calculating infiltration practice drainage time== |
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| | Try the Darcy drainage time calculator tool for estimating the time required to fully drain the water storage reservoir of the facility assuming either one or three-dimensional drainage: <br> |
| | {{Clickable button|[[Media:Darcy drainage_20200528_locked.xlsx|Download the Darcy drainage time calculator tool]]}} |
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| [[File:Interevent times.PNG|thumb|https://public.tableau.com/views/StormIntereventTimesOntario/Sheet1?:embed=y&:display_count=yes&publish=yes]] | | ==See also== |
| | [[Understanding rainfall statistics]] |
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| | ---- |
| | [[Category:Infiltration]] |
| | [[Category: Background]] |