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| [[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]]. |
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− | 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 saturated hydraulic conductivity of the filter media and the number and size of perforations of the [[underdrain]] pipe play critical roles for flow control. Options for maintaining separation between filter media and clear stone aggregate surrounding the perforated pipe include a 100 mm deep choker layer or sheet of geotextile filter fabric. |
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| {| class="wikitable" | | {| class="wikitable" |
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| ! 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 |
| |- | | |- |
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| * 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 | + | | |
| + | * 0.4 for sandier Blend A - Drainage rate priority; |
| + | * 0.35 for more loamy Blend B - Water quality treatment priority |
| |- | | |- |
− | | Pipe diameter reservoir | + | | Choker layer |
− | | Is equal to underdrain [[pipe]] diameter | + | | 100 mm |
| + | | 0.4 |
| + | |- |
| + | | Perforated pipe diameter |
| + | | 150 to 200 mm |
| | 0.4 | | | 0.4 |
| |- | | |- |
− | | [[Choker course|Pipe bedding]] (''d<sub>b</sub>'') | + | | Clear stone aggregate layer below perforated pipe |
| | 50 mm (although commonly omitted altogether). | | | 50 mm (although commonly omitted altogether). |
| | 0.4 | | | 0.4 |
| |} | | |} |
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− | ==Calculate the maximum overall depth==
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