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Line 1: + + + + + + + + + + + + + + + + + + + + + + + − <div class='tableauPlaceholder' id='viz1504792826443' style='position: relative'><noscript><a href='https://wiki.sustainabletechnologies.ca/index.php/Drawdown_time'><img alt='Sheet 1 ' src='https://public.tableau.com/static/images/St/StormIntereventTimesOntario/Sheet1/1_rss.png' style='border: none' /></a></noscript><object class='tableauViz' style='display:none;'><param name='host_url' value='https%3A%2F%2Fpublic.tableau.com%2F' /> <param name='site_root' value='' /><param name='name' value='StormIntereventTimesOntario/Sheet1' /><param name='tabs' value='no' /><param name='toolbar' value='yes' /><param name='static_image' value='https://public.tableau.com/static/images/St/StormIntereventTimesOntario/Sheet1/1.png' /> <param name='animate_transition' value='yes' /><param name='display_static_image' value='yes' /><param name='display_spinner' value='yes' /><param name='display_overlay' value='yes' /><param name='display_count' value='yes' /><param name='filter' value='publish=yes' /></object></div> <script type='text/javascript'> var divElement = document.getElementById('viz1504792826443'); var vizElement = divElement.getElementsByTagName('object')[0]; vizElement.style.width='100%';vizElement.style.height=(divElement.offsetWidth*0.75)+'px'; var scriptElement = document.createElement('script'); scriptElement.src = 'https://public.tableau.com/javascripts/api/viz_v1.js'; vizElement.parentNode.insertBefore(scriptElement, vizElement); </script>+ + + + + + + + +
→Calculating infiltration practice drainage time
[[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.]]
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).
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>
==Calculating infiltration practice drainage time==
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]]}}
==See also==
[[Understanding rainfall statistics]]
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[[Category:Infiltration]]
[[Category: Background]]