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The most common form of weir in LID practices is a rectangular weir, in the form of a [[check dam]] or flow control in a [[swale]] or other open channel.
The most common form of weir in LID practices is a rectangular weir, in the form of a [[check dam]] or flow control in a [[swale]] or other open channel.
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The flow (Q), may be calculated by measuring the height of water on the sill of the weir:
The flow (Q), may be calculated by measuring the height of water on the sill of the weir:
<math>Q=\frac{2}{3}C_{d}\cdot L\sqrt{2g}\cdot H^{\frac{3}{2}}</math>
<math>Q=\frac{2}{3}C_{d}\cdot L\sqrt{2g}\cdot H^{\frac{3}{2}}</math>
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{{Plainlist|1=Where:
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*''C<sub>d</sub>'' = discharge coefficient (default 0.62 for a 'sharp edge).
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*''L'' = Length of the weir (m)
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*''g'' = Acceleration due to gravity (9.81 m/s<sup>2</sup>)
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*''H'' = Height of water over the weir (m)}}
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==More flow related pages==
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*[[Flow in a swale]]
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*[[Flow through perforated pipe]]
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*[[Flow through an orifice]]