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→Time to drain internal water storage reservoir
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<imagemap>
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Image:Infiltration.png|thumb|700 px|This is an image map; clicking on components will load the appropriate article.
Image:Infiltration.png|thumb|500 px|This is an image map; clicking on components will load the appropriate article.
poly 315 507 208 555 317 605 423 555 [[Drainage time]]
poly 315 507 208 555 317 605 423 555 [[Drainage time]]
rect 210 658 426 730 [[Details]]
rect 210 658 426 730 [[Details]]
|''A<sub>i''||m<sup>2</sup>||Catchment impervious area
|''A<sub>i''||m<sup>2</sup>||Catchment impervious area
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|''d<sub>r</sub>''||m||Water storage reservoir depth. For practices without an underdrain (i.e. full infiltration design), d<sub>r</sub> is the total depth of the practice (i.e. includes surface ponding and filter media depths). For practices with an underdrain (i.e. partial infiltration design), d<sub>r</sub> is the depth below the invert of the underdrain perforated pipe outlet.
|''d<sub>r</sub>''||m||Water storage reservoir depth. For practices without an underdrain (i.e. full infiltration design), d<sub>r</sub> is the total depth of the practice (i.e. includes surface ponding and filter media depths). For practices with an underdrain (i.e. partial infiltration design), d<sub>r</sub> is the depth below the invert of the underdrain perforated pipe or riser pipe upturn.
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|''A<sub>p</sub>''||m<sup>2</sup>||Permeable footprint area of the practice. For practices where runoff is directed to a surface ponding area, A<sub>p</sub> is the surface ponding area. For practices where runoff is directed to a subsurface water storage reservoir, A<sub>p</sub> is the footprint area of the storage reservoir, A<sub>r</sub>
|''A<sub>p</sub>''||m<sup>2</sup>||Permeable footprint area of the practice. For practices where runoff is directed to a surface ponding area, A<sub>p</sub> is the surface ponding area. For practices where runoff is directed to a subsurface water storage reservoir, A<sub>p</sub> is the footprint area of the internal water storage reservoir, A<sub>r</sub>.
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|''x''||m||Perimeter of the practice
|''x''||m||Perimeter of the practice
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|''K<sub>f</sub>''||m/h||Minimum acceptable saturated hydraulic conductivity of the [[Bioretention: Filter media|filter media]] or [[Topsoil| planting soil]] used in the practice, when compacted to 85% maximum dry density
|''K<sub>f</sub>''||m/h||Minimum acceptable saturated hydraulic conductivity of the [[Bioretention: Filter media|filter media]] or growing medium (i.e., planting soil) used in the practice, when compacted to 85% maximum dry density
|}
|}
This spreadsheet tool has been set up to perform all of the infiltration practice sizing calculations shown below<br>
This spreadsheet tool has been set up to perform all of the infiltration practice sizing calculations shown below<br>
{{Clickable button|[[Media:Infiltration Sizing 20200525 locked.xlsx|Download the infiltration practice sizing tool]]}}
{{Clickable button|[[Media:Infiltration Sizing 20220617 locked (1).xlsx|Download the infiltration practice sizing tool]]}}
==To calculate the required storage reservoir footprint area where the depth is fixed or constrained (1D drainage)==
==To calculate the required storage reservoir footprint area where the depth is fixed or constrained (1D drainage)==
==Time required to drain surface ponded water (1D drainage)==
==Time required to drain surface ponded water (1D drainage)==
The following equation assumes one dimensional drainage over the surface ponding area.
The following equations assume one dimensional drainage over the surface ponding area.
It is best applied to calculate the maximum duration of ponding on the surface of [[Bioretention |bioretention cells]] and [[Stormwater Tree Trenches |stormwater tree trenches]], and upstream of check dams of [[bioswales]] and [[enhanced grass swales]] to ensure all surface ponding drains within 24 hours.
It is best applied to calculate the maximum duration of ponding on the surface of [[Bioretention |bioretention cells]] and [[Stormwater Tree Trenches |stormwater tree trenches]], and upstream of check dams of [[bioswales]] and [[enhanced grass swales]] to ensure all surface ponding drains within 24 hours.<br>
To calculate the time (''t'') to fully drain surface ponded water through the filter media or growing medium:
To calculate the time (''t'') to fully drain surface ponded water through the filter media or growing medium:
<math>t=\frac{d_{p}'}{K_{f}}</math>
<math>t=\frac{d_{p}'}{K_{f}}</math> <br>
Where <br>
Where <br>
d<sub>p</sub>' is the effective or mean surface ponding depth (mm).<br>
d<sub>p</sub>' is the effective or mean surface ponding depth (mm).<br>
K<sub>f</sub> is the minimum acceptable saturated hydraulic conductivity of the filter media or planting soil when compacted to 85% maximum dry density (mm/h); minimum of 25 mm/hr is recommended for bioretention filter media; minimum of 15 mm/hr is recommended for enhanced swale and stormwater tree trench growing medium.
K<sub>f</sub> is the minimum acceptable saturated hydraulic conductivity of the filter media and growing medium when compacted to 85% maximum dry density (mm/h); minimum of 25 mm/hr is recommended for bioretention filter media; minimum of 15 mm/hr is recommended for enhanced grass swale and stormwater tree trench growing medium.<br>
<br>
For full infiltration design practices that do not feature an underdrain, once the internal water storage capacity has been filled, the length of time required to fully drain surface ponded water is limited by the saturated hydraulic conductivity of the underlying in-situ (native) subsoil. To calculate the time (''t'') to fully drain surface ponded water once filled to capacity:
<math>t=\frac{d_{p}'}{f'}</math> <br>
Where <br>
d<sub>p</sub>' is the effective or mean surface ponding depth (mm).<br>
f' is the design infiltration rate of the underlying native soil.
==Time to drain internal water storage reservoir==
==Time to drain internal water storage reservoir==
From left to right x = 12 m, x = 20 m]]<br>
From left to right x = 12 m, x = 20 m]]<br>
For some geometries, particularly deep or linear facilities, it desirable to account for lateral drainage, out the sides of the storage reservoir.
For some geometries, particularly deep or linear facilities, it desirable to account for lateral drainage, out the sides of the storage reservoir.
The following equation makes use of the hydraulic radius (''A<sub>r''/''x''), where ''A<sub>r'' is the area of the reservoir and ''x'' is the perimeter (m) of the reservoir. <br>
The following equation makes use of the hydraulic radius (''A<sub>r</sub>''/''x''), where ''A<sub>r</sub>'' is the area of the reservoir and ''x'' is the perimeter (m) of the reservoir. <br>
'''Maximizing the perimeter of the water storage reservoir of the facility will enhance drainage performance and directs designers towards longer, linear shapes such as [[infiltration trenches]] and [[bioswales]].''' See illustration for an example.<br>
'''Maximizing the perimeter of the water storage reservoir of the facility will enhance drainage performance and directs designers towards longer, linear shapes such as [[infiltration trenches]] and [[bioswales]].''' See illustration for an example.<br>
<math>t=\frac{n\times A_{r}}{f'\times x}ln\left [ \frac{\left (d_{r} + \frac{A_{r}}{x} \right)}{\left (\frac{A_{r}}{x}\right) }\right]</math>
<math>t=\frac{n\times A_{r}}{f'\times x}ln\left [ \frac{\left (d_{r} + \frac{A_{r}}{x} \right)}{\left (\frac{A_{r}}{x}\right) }\right]</math>
Where "ln" means natural logarithm of the term in square brackets <br>
Where "ln" means natural logarithm of the term in square brackets <br>
Adapted from CIRIA, The SUDS Manual C753 (2015).
Adapted from CIRIA, The SUDS Manual C753 (2015)<ref>Construction Industry Research and Information Association (CIRIA). 2015. The SUDS Manual C753. Accessed: 18 November 2021. https://www.ciria.org/CIRIA/Memberships/The_SuDs_Manual_C753_Chapters.aspx</ref>
[[category: modeling]]
[[category: modeling]]
[[category: infiltration]]
[[category: infiltration]]