Bioretention media is designed to incorporate different media types – including mulch, compost, soil, sand, and gravel. This layered media supports plant growth, provides biofiltration capabilities, and is designed to meet hydrological requirements.
As stormwater is redirected through a bioretention system, it is retained in a temporary ponding layer and allowed to infiltrate the layered media underneath. The infiltration qualities of the system, and their ability to soak in stormwater help to mitigate flooding.
A bioretention system’s physical, chemical and biological processes all contribute to stormwater treatment – which occurs as stormwater is conveyed and allowed to infiltrate the media layers. Sustainable green assets can help to increase urban amenities and clean polluted stormwater discharge.
Plants in bioretention systems are generally selected for their pollution removal capabilities and have been shown to improve dissolved nutrient removal, remove hydrocarbons, and aid TSS sequestration. The root networks of these plants also help to keep the media permeable.
Bioretention allows treatment to occur across its various layers and provides many benefits –
- WSUD (Water Sensitive Urban Design) compliance
- Development of green infrastructure & sustainable stormwater assets
- Pollutant removal, increased water quality & stormwater treatment
- Reduced stormwater run-off velocities
- Flood mitigation & management of water quantity
- Increase in permeable surface and infiltration
