Changes

During a 25 mm storm event, a bioretention cell receives concentrated flow from a catchment 20 times larger than its own footprint (25 x 20 = 500 mm = 0.5 m).  

During a 25 mm storm event, a bioretention cell receives concentrated flow from a catchment 20 times larger than its own footprint (25 x 20 = 500 mm = 0.5 m).  

The bioretention cell comprises 0.6 m filter media laid over 0.6 m clear, coarse reservoir gravel. The pipes are laid within the reservoir, 0.9 m below the surface.  

The bioretention cell comprises 0.6 m filter media laid over 0.6 m clear, coarse reservoir gravel. The pipes are laid within the reservoir, 0.9 m below the surface.  

The system is designed to fill entirely during the rainstorm event. i.e. Depth to water table = 0 m.     

The system is designed to fill entirely during the rainstorm event. i.e. Depth to water table = 0 m.:    

<math>Drain\ spacing=\sqrt{\frac{4\times 2.4m\left(0.9m-0m\right)^{2}}{0.5}}=6 m</math>

<math>Drain\ spacing=\sqrt{\frac{4\times 2.4m\left(0.9m-0m\right)^{2}}{0.5}}=6 m</math>