Difference between revisions of "Level spreaders"
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[[File:Level spreader diagram.jpg|thumb|Diagram from Wikimedia commons. Credit: U.S. Army Corps of Engineers, Construction Engineering Research Laboratory]] | [[File:Level spreader diagram.jpg|thumb|Diagram from Wikimedia commons. Credit: U.S. Army Corps of Engineers, Construction Engineering Research Laboratory]] | ||
Level spreaders should conform to the following design criteria in order to ensure non-erosive sheet flow into vegetated areas such as [[vegetated filter strips]], | Level spreaders should conform to the following design criteria in order to ensure non-erosive sheet flow into vegetated areas such as [[vegetated filter strips]], [[Bioretention|bioretention]], [[swales]] or forested conservation areas<ref>Hathaway, J. M., & Hunt, W. F. (2006). Level Spreaders : Overview , Design , and Maintenance.</ref>. | ||
The length of the level spreader should be determined by the type of | The length of the level spreader should be determined by the design storm inflow rate and type of landscape downstream: | ||
* 1.4 m of level spreader length per every 0.01 m³/s of inflow | * 1.4 m of level spreader length per every 0.01 m³/s of inflow when draining to a [[vegetated filter strips|vegetated filter strip]], [[Bioretention| bioretention]], [[Swale| swale]] or grassed area; | ||
* 4.3 m of level spreader length per every 0.01 m³/s of inflow when | * 4.3 m of level spreader length per every 0.01 m³/s of inflow when draining to a forested conservation area. | ||
* The minimum level spreader length is 4 m and the maximum is 40 m. | * The minimum level spreader length is 4 m and the maximum is 40 m. | ||
* The level spreader lip should be concrete, wood or pre-fabricated metal | * The level spreader lip should be concrete, wood or pre-fabricated metal. | ||
* The ends of the level spreader section should be tied back into the slope to avoid [[overflow]] scouring or erosion around the ends | * The ends of the level spreader section should be tied back into the slope to avoid [[overflow]] scouring or erosion around the ends. | ||
* | * The width of the level spreader should be the greater of 300 mm or three times the diameter of the inflow pipe. | ||
* The depth should be the greater of 200 mm or half the inflow pipe diameter. | |||
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Latest revision as of 01:49, 15 July 2020
This clever design incorporates a level spreading device after a curb cut has narrowed the flow path. This kind of treatment train approach would provide an opportunity to provide pretreatment at the point of concentration. Photo credit: MPCA
Level spreaders should conform to the following design criteria in order to ensure non-erosive sheet flow into vegetated areas such as vegetated filter strips, bioretention, swales or forested conservation areas[1].
The length of the level spreader should be determined by the design storm inflow rate and type of landscape downstream:
- 1.4 m of level spreader length per every 0.01 m³/s of inflow when draining to a vegetated filter strip, bioretention, swale or grassed area;
- 4.3 m of level spreader length per every 0.01 m³/s of inflow when draining to a forested conservation area.
- The minimum level spreader length is 4 m and the maximum is 40 m.
- The level spreader lip should be concrete, wood or pre-fabricated metal.
- The ends of the level spreader section should be tied back into the slope to avoid overflow scouring or erosion around the ends.
- The width of the level spreader should be the greater of 300 mm or three times the diameter of the inflow pipe.
- The depth should be the greater of 200 mm or half the inflow pipe diameter.
- ↑ Hathaway, J. M., & Hunt, W. F. (2006). Level Spreaders : Overview , Design , and Maintenance.