Difference between revisions of "Flow through media"
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The maximum flow rate from the BMP may be limited by the hydraulic conductivity of the mmedium, or by the properties of the perforated [[pipe]]. | The maximum flow rate from the BMP may be limited by the hydraulic conductivity of the mmedium, or by the properties of the perforated [[pipe]]. | ||
| − | The maximum flow rate through a bed of filer media (''Q<sub>max</sub>'') may be calculated: | + | The maximum flow rate through a bed of filer media (''Q<sub>max</sub>'', L/s) may be calculated: |
<math>Q_{max}=\frac{K_{m}\times A_{p}\times \left (\frac{\sum d}{d_{m}} \right )}{3600}</math> | <math>Q_{max}=\frac{K_{m}\times A_{p}\times \left (\frac{\sum d}{d_{m}} \right )}{3600}</math> | ||
{{Plainlist|1=Where: | {{Plainlist|1=Where: | ||
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===Example calculation=== | ===Example calculation=== | ||
| − | A [[stormwater planter]] with footprint of 8 x 1.5 m is planned to received runoff from an adjacent rooftop. The initial design for the planters includes 750 mm depth of filter medium, 50 mm rock mulch, and a further ponding of 300 mm. The underdrain pipe will be embedded into high performance bedding or similar, with a strip of geotextile over the top to prevent migration of the filter media into the pipe. The lab test states that the medium has a hydraulic conductivity of 25 mm/hr. The maximum flow through the medium will be calculated and a comparison made with the maximum flow through the pipe to see.... | + | A [[stormwater planter]] with footprint of 8 x 1.5 m is planned to received runoff from an adjacent rooftop. The initial design for the planters includes 750 mm depth of filter medium, 50 mm rock mulch, and a further ponding of 300 mm. The underdrain pipe will be embedded into high performance bedding or similar, with a strip of geotextile over the top to prevent migration of the filter media into the pipe. The lab test states that the medium has a hydraulic conductivity of 25 mm/hr. The maximum flow through the medium will be calculated and a comparison made with the maximum flow through the pipe to see....: |
<math>Q_{max}=\frac{25 mm/hr\times 12\ m^{2}\times \left (\frac{1.1\ m}{0.75\ m} \right )}{3600\ s/hr}</math> | <math>Q_{max}=\frac{25 mm/hr\times 12\ m^{2}\times \left (\frac{1.1\ m}{0.75\ m} \right )}{3600\ s/hr}</math> | ||
Revision as of 16:05, 25 February 2018
Practices which infiltrate surface runoff through an engineered soil or filter media, and discharge through an underdrain include stormwater planters and some forms of bioretention. The maximum flow rate from the BMP may be limited by the hydraulic conductivity of the mmedium, or by the properties of the perforated pipe.
The maximum flow rate through a bed of filer media (Qmax, L/s) may be calculated:
Where:
- Km is the hydraulic conductivity of the filter media (mm/hr),
- Ap is the area of the practice (m2),
- Σ d is the total depth of bioretention components over the perforated pipe (mm) (e.g. ponding/mulch/filter media/choker layer), and
- dm is the depth of the filter media (mm).
Example calculation[edit]
A stormwater planter with footprint of 8 x 1.5 m is planned to received runoff from an adjacent rooftop. The initial design for the planters includes 750 mm depth of filter medium, 50 mm rock mulch, and a further ponding of 300 mm. The underdrain pipe will be embedded into high performance bedding or similar, with a strip of geotextile over the top to prevent migration of the filter media into the pipe. The lab test states that the medium has a hydraulic conductivity of 25 mm/hr. The maximum flow through the medium will be calculated and a comparison made with the maximum flow through the pipe to see....:
