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Forebays are a form of [[pretreatment]] for open inlets such as [[curb cuts]]. Energy of the incoming flow is dissipated, causing suspended particles to drop out of the water. These accumulated particles/sediment can then be easily swept or vacuumed during routine maintenance and doesn't end up clogging downstream filter media or material.
Forebays are a form of [[pretreatment]] for open inlets such as [[curb cuts]]. Energy of the incoming flow is dissipated, causing suspended particles to drop out of the water. These accumulated particles/sediment can then be easily swept or vacuumed during routine maintenance and doesn't end up clogging downstream filter media or material.
A well designed forebay will also spread the flow somewhat, reducing erosion around the inlet. One effective way of achieving this is by surrounding the pad with some form of level spreader on all sides. The level spreading could be a sharp crested weir in metal or concrete, or be more like a soft edged [[Check dams|check dam]].
A well designed forebay will also spread the flow somewhat, reducing erosion around the inlet. One effective way of achieving this is by surrounding the pad with some form of level spreader on all sides. The level spreading could be a sharp crested weir in metal or concrete, or be more like a soft edged [[Check dams|check dam]].
The required volume for a small forebay serving up to 2 Ha (''V<sub>f</sub>'', m³) may be calculated as:
<math>V_{f}=A_{c}\times R\times L_{o} \times F_{c}</math>
{{plainlist| 1=Where:
*''A<sub>c</sub>'' = The area of the catchment (m²),
*''R'' = The capture efficiency (suggest 0.8),
*''L<sub>o</sub>'' = The sediment loading rate (m³/Ha/yr), and
*''F<sub>c</sub> = The cleanout frequency (yrs)
}}
==Gallery==
{{:Forebays:_Gallery}}
{{:Forebays:_Gallery}}
[[Category:Pretreatment]]
[[Category:Pretreatment]]