Difference between revisions of "Enhanced grass swales"
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*[[Liner|Impermeable membrane]], to prevent infiltration to soils below | *[[Liner|Impermeable membrane]], to prevent infiltration to soils below | ||
*[[Turf reinforcement]], to prevent scour | *[[Turf reinforcement]], to prevent scour | ||
| + | |||
| + | ==Planning considerations== | ||
==Design== | ==Design== | ||
| + | Swales should be designed to meet the following criteria: | ||
*Minimum residence time of 5 minutes. | *Minimum residence time of 5 minutes. | ||
*Maximum flow velocity 0.3 m/s | *Maximum flow velocity 0.3 m/s | ||
*Bottom width between 0.6 - 2.4 m | *Bottom width between 0.6 - 2.4 m | ||
*Minimum length 30 m | *Minimum length 30 m | ||
| − | |||
{|class="wikitable" | {|class="wikitable" | ||
|+ Slope variations | |+ Slope variations | ||
| Line 28: | Line 30: | ||
||5 %||Check dams required to reduce effective slope to 2 – 3 % | ||5 %||Check dams required to reduce effective slope to 2 – 3 % | ||
|} | |} | ||
| − | |||
Maximum depth of flow | Maximum depth of flow | ||
{{plainlist| | {{plainlist| | ||
| Line 34: | Line 35: | ||
*33% height of vegetation for infrequently mown swales. | *33% height of vegetation for infrequently mown swales. | ||
|}} | |}} | ||
| + | |||
| + | <h3>Materials</h3> | ||
Revision as of 23:56, 7 September 2017
This article is about installations designed to capture and convey surface runoff along a vegetated channel, whilst also promoting infiltration.
For underground conveyance which promotes infiltration, see Exfiltration trenches.
For conveyance along planted channels, on both surface and underground, see Bioswales.
Overview[edit]
The fundamental components of an enhanced grassed swale are:
- Graded channel
- Resilient turf grass
- Check dams, to facilitate short term ponding
Additional components may include:
- Amended soil, to increase infiltration to soils below
- Impermeable membrane, to prevent infiltration to soils below
- Turf reinforcement, to prevent scour
Planning considerations[edit]
Design[edit]
Swales should be designed to meet the following criteria:
- Minimum residence time of 5 minutes.
- Maximum flow velocity 0.3 m/s
- Bottom width between 0.6 - 2.4 m
- Minimum length 30 m
| < 2 % | Use underdrain to distribute water for infiltration |
| 2 - 5 % | Design swale for surface flow, consider check dams |
| 5 % | Check dams required to reduce effective slope to 2 – 3 % |
Maximum depth of flow
- 50% height of grass for regularly mown swales, to maximum of 75 mm.
- 33% height of vegetation for infrequently mown swales.