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Line 35: + + + + + + − ==Planning Considerations==+ − <div class="col-md-8">+ − A linear design (surface area typically >2:1 length:width) is a common feature of a swales:+ − <ul> − <li>An absolute minimum width is 0.6 m is required for bioswales to have healthy plant growth, and to facilitate construction. </li> − <li>Grassed swales are usually mown as part of routine maintenance, so the cross section will be parabolic or trapzoidal in shape. The minimum width for this type is 2 m. </li> − </ul> − Swales may be graded along longitudinal slopes between 0.5 - 6 %: − <ul> − <li>Check dams are required on slopes > 3 %. </li> − <li>Slopes > 6% can accommodate a series of stepped [[bioretention cells]], each overflowing into the next with a weir. </li> − </ul> − </div> − <div class="col-md-4"> − <panelWarning> − <gallery mode="packed" widths=300px heights=300px> − Bioswale.png| Bioswale with check dams<br> (vertical scale exaggerated) − Stepped cells.png| Stepped bioretention cells alternative for slopes >6 % − </gallery> − </panelWarning> − </div> − <div class="col-md-12"> − − <div class="col-md-8"> Line 75:
Line 60: − <ul>+ − <li>[[Underdrain]]</li>+ − <li>[[Bioretention: Filter media]]</li> − </ul>
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==Planning Considerations==
[[File:Bioswale.png||thumb|Bioswale with check dams<br> (vertical scale exaggerated)]]
[[File:Stepped cells.png||thumb|Stepped bioretention cells alternative for slopes >6 %]]
A linear design (surface area typically >2:1 length:width) is a common feature of a swales:
*An absolute minimum width is 0.6 m is required for bioswales to have healthy plant growth, and to facilitate construction,
*Grassed swales are usually mown as part of routine maintenance, so the cross section will be parabolic or trapzoidal in shape. The minimum width for this type is 2 m.
Swales may be graded along longitudinal slopes between 0.5 - 6 %:
*Check dams are required on slopes > 3 %.
*Slopes > 6% can accommodate a series of stepped [[bioretention cells]], each overflowing into the next with a weir.
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==Design==
==Design==
<h3>Pretreatment and inlets</h3>
<h3>Pretreatment and inlets</h3>
<p>To minimize erosion and maximize the functionality of the swale, sheet flow of surface water should be directed into the side of the BMP. [[Gravel diaphragms]], [[vegetated filter strips]] and shallow side slopes are ideal. Alternatively, a series of curb inlets can be employed, where each has some form of flow spreading incorporated. Single point inflow can cause increased erosion and sedimentation which will damage vegetation and contribute to BMP failure. Again, flow spreading devices can mitigate these processes, where concentrated point inflow is required. </p>
<p>To minimize erosion and maximize the functionality of the swale, sheet flow of surface water should be directed into the side of the BMP. [[Gravel diaphragms]], [[vegetated filter strips]] and shallow side slopes are ideal. Alternatively, a series of curb inlets can be employed, where each has some form of flow spreading incorporated. Single point inflow can cause increased erosion and sedimentation which will damage vegetation and contribute to BMP failure. Again, flow spreading devices can mitigate these processes, where concentrated point inflow is required. </p>
*Energy dissipation and erosion control measures should be installed in the 1 - 2 m downstream of each dam. Examples include large aggregate or [[Turf reinforcement|turf reinforcement]]
*Energy dissipation and erosion control measures should be installed in the 1 - 2 m downstream of each dam. Examples include large aggregate or [[Turf reinforcement|turf reinforcement]]
<h4>Other components</h4>
<h4>Other components</h4>
*[[Underdrain]]
*[[Bioretention: Filter media]]
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