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Line 19: − + − + − + − + + + − − + − + − − − ==Calculate the maximum overall depth== − *Step 1: Determine what the planting needs are and assign appropriate depth of media, using the table above. − *Step 2: Select an underdrain pipe diameter (typically 100 - 200 mm), assign this as an 'embedding' depth. − *Step 3: Calculate the maximum possible storage reservoir depth beneath the pipe (''d<sub>s</sub>''): − <math>d_{s}=f'\times38.4</math> − {{Plainlist|1=Where: − *''f''' = Design infiltration rate in mm/hr, and − *38.4 comes from multiplying desired drainage time of 96 hours by void ratio of 0.4}} − − ===Additional step for system without underdrain=== − *Step 4: Determine maximum permissible ponding depth (''d<sub>p</sub>''): − <math>d_{p}=f'\times19.2</math> − {{Plainlist|1=Where: − *''f''' = Design infiltration rate in mm/hr, and − *19.2 comes from multiplying desired drainage time of 48 hours by void ratio of 0.4. Note that conceptually the drainage of the ponded area is limited by ex-filtration at the base of the practice.}} − * Step 5: Sum total depth of bioretention, and compare to available space above water table and bedrock. Adjust if necessary. − − ==Calculate the remaining dimensions== − * Step 6: Multiply the depth of each separate component by the void ratio and then sum the total to find the 1 dimensional storage (in mm). − * Step 7: Calculate the required total storage (m<sup>3</sup>): − <math>Storage=RVC_T\times A_c\times C\times 0.1</math> − {{Plainlist|1=Where: − *''RVC<sub>T</sub>'' is the Runoff volume control target (mm), − *''A<sub>c</sub>'' is the catchment area (Ha), − *''C'' is the runoff coefficient of the catchment area, and − * 0.1 is the units correction between m<sup>3</sup> and mm.Ha.}} − * Step 8. Divide required storage (m<sup>3</sup>) by the 1 dimensional storage (in m) to find the required footprint area (''A<sub>p</sub>'') for the bioretention in m<sup>2</sup>. − * Step 9. Calculate the peak flow rate (''Q<sub>p</sub>'', in L/s) through the filter media: − ----
no edit summary
[[File:Sizing flow-through planter.jpg|thumb|A flow-through planter comprises a ponding zone, mulch layer, filter media for planting, and a supporting gravel drainage layer]]
[[File:Sizing flow-through planter.jpg|thumb|A flow-through planter comprises a ponding zone, mulch layer, filter media for planting, and a supporting gravel drainage layer]]
This article is specific to [[Flow-through stormwater planters]], vegetated systems that do not infiltrate water to the native soil. <br>
This article is specific to flow-through [[Stormwater planters|stormwater planters]], vegetated systems that do not infiltrate water to the native soil. <br>
If you are designing a planted system which does infiltrate water, see advice on [[Bioretention: Sizing]].
If you are designing a planted system which does infiltrate water, see advice on [[Bioretention: Sizing]].
The dimensions of a stormwater planter are largely predetermined according to the function of the component. As they do not contain a storage reservoir the planters rely more upon careful selection of materials. Both the filter media and the perforations of the pipe play critical roles for flow control.
The dimensions of a stormwater planter are largely predetermined according to the function of the component. As they do not contain a storage reservoir the planters rely more upon careful selection of materials. Both the filter media and the perforations of the [[Pipe| pipe]] play critical roles for flow control.
{| class="wikitable"
{| class="wikitable"
! Component
! Component
! Recommended depth (with underdrain pipe)
! Recommended depth (with underdrain pipe)
! Typical void ratio (''V<sub>R</sub>'')
! Typical porosity (''n'')
|-
|-
| Ponding (''d<sub>p</sub>'')
| Ponding (''d<sub>p</sub>'')
| ≥ 300 mm
| 150 to 450 mm
| 1
| 1
|-
|-
|
|
* 0.7 for wood based
* 0.7 for wood based
* 0.4 for aggregate
* 0.4 for stone
|-
|-
| [[Bioretention: Filter media|filter media]] (''d<sub>m</sub>'')
| [[Bioretention: Filter media|Filter media]] (''d<sub>m</sub>'')
|
|
* 300 mm to support turf grass (and accept only rainwater/roof runoff)
* 300 mm to support turf grass (and accept only rainwater/roof runoff)
* 600 mm to support flowering [[perennials]] and decorative [[grasses]]
* 600 mm to support shrubs, flowering [[perennials]] and decorative [[grasses]]
* 1000 mm to support [[trees]]
* 1000 mm to support [[trees]]
| 0.3
|
* 0.35 for Blend A - Drainage rate priority;
* 0.4 for Blend B - Water quality treatment priority
|-
|-
| Pipe diameter reservoir
| Pipe diameter reservoir
| Is equal to underdrain pipe diameter
| Is equal to underdrain [[pipe]] diameter
| 0.4
| 0.4
|-
|-
| Pipe bedding (''d<sub>b</sub>'')
| [[Choker course|Pipe bedding]] (''d<sub>b</sub>'')
| 50 mm (although commonly omitted altogether).
| 50 mm (although commonly omitted altogether).
| 0.4
| 0.4
|}
|}