Flow through perforated pipe

Manufacturers of perforated pipe are often able to provide the open area (m²) per meter length.

$Q_{max,p}=B\times C_{d}\times A_{o}{\sqrt {2\cdot g\cdot \sum d}}$

Where:_d is the coefficient of discharge (0.61 for a sharp edged orifice),

• B is the clogging factor (between 0.5 to calculate a for matured installation and 1 to calculate a new perfectly performing BMP),
• C_d is the coefficient of discharge (usually 0.61 for the sharp edge created by relatively thin pipe walls),
• A_o is the total open area per unit length of pipe (m²/m),
• g is acceleration due to gravity (m/s²)
• Σ d is the total depth of bioretention components over the perforated pipe (mm) (e.g. ponding/mulch/filter media/choker layer),
• O is the number of orifices per meter of perforated pipe.

Best management practice. State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include: source, conveyance and end-of-pipe controls.

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.