This article is specific to Flow-through stormwater planters, vegetated systems that do not infiltrate water to the native soilThe natural ground material characteristic of or existing by virtue of geographic origin..
If you are designing a planted system which does infiltrate water, see advice on Bioretention: Sizing.
The dimensions of a stormwater planterA vegetated practice that collects and treats stormwater through sedimentation and filtration. Contributions to water cycle/water balance are through evapotranspiration only; no infiltration. 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 mediaThe engineered soil component of bioretention cell or dry swale designs, typically with a high rate of infiltration and designed to retain contaminants through filtration and adsorption to particles. and the perforations of the pipe play critical roles for flow control.
|Component||Recommended depth (with underdrainA perforated pipe used to assist the draining of soils. pipe)||Typical void ratio (VR)|
|Ponding (dp)||≥ 300 mm||1|
|Mulch||75 ± 25 mm||
|filter media (dm)||
|Pipe diameter reservoir||Is equal to underdrainA perforated pipe used to assist the draining of soils. pipe diameter||0.4|
|Pipe bedding (db)||50 mm (although commonly omitted altogether).||0.4|