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===Example calculation===
===Example calculations===
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 is calculated and then a comparison made with the maximum flow through the pipe to see if the planter will drain freely.
<math>Q_{max, m}=\frac{25 mm/hr\times 12\ m^{2}\times \left (\frac{1.1\ m}{0.75\ m} \right )}{3600\ s/hr}=0.12\ L/s</math>
<math>Q_{max, m}=\frac{25 mm/hr\times 12\ m^{2}\times \left (\frac{1.1\ m}{0.75\ m} \right )}{3600\ s/hr}=0.12\ L/s</math>
A [[bioretention]] cell with footprint of 30 x 10 m is planned to received runoff from adjacent roadways and parking facilities. The design includes 600 mm depth of filter medium, 75 mm wood based mulch, and ponding of 300 mm. Two underdrain pipes will be embedded at the base of the storage reservoir. These will connect together and then have an upturn within a manhole at the downstream end to prevent discharge until the head of water reaches the top of the storage reservoir within the cell. The lab test for the filter medium state that it has a hydraulic conductivity of 80 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, m}=\frac{80 mm/hr\times 300\ m^{2}\times \left (\frac{0.975\ m}{0.6\ m} \right )}{3600\ s/hr}=10.8\ L/s</math>