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Typical stone functions in LID and direction on selection:
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[[File: IMAX_Stone_Inlet.jpeg|thumb|This bioswale in a parking lot uses stone at the inlets and along the bottom of the swale to prevent erosion, as the sides are sloped.]]
[[File: IMAX_Stone_Inlet.jpeg|thumb|This bioswale in a parking lot uses stone at the inlets and along the bottom of the swale to prevent erosion, as the sides are sloped.]]
For advice on aggregates used in [[Underdrains|underdrains]], see [[Gravel|gravel]]
Stone or gravel can serve as a low maintenance decorative feature, but it may also serve many practical functions in an LID practice. For advice on aggregates used in [[Underdrains|underdrains]], see [[Gravel|gravel]]
Stone can serve as a low maintenance decorative feature, but it may also serve practical functions in an LID practice.
{|class="wikitable"
|+ Stone functions and specifications
!style="background: darkcyan; color: white"|Function
Dissipate flow and prevent erosion at inlets and outlets
!style="background: darkcyan; color: white"|Recommended Specification
|-
|Subsurface storage layer for stormwater and to surround the underdrain or subdrain
|
*50mm diameter clear stone, washed and free of all fines, should be used
*The depth of the gravel subsurface storage layer is a minimum of 300 mm and the underdrain is set at least 100 mm above the bottom to provide a minimum infiltration volume
*A 100 mm pea gravel choking layer and optional drainage geotextile can be used to prevent the bioretention soil from migrating into the gravel storage layer and underdrain
*Geotextile is not recommended around the sides and bottom of the gravel storage layer as it has been found to be unnecessary and a common cause of early clogging
|-
|Dissipate flow and prevent erosion at inlets and outlets
|
*Angular crushed stone, which will "knit" or lock together and be less likely to shift, is recommended. However, for aesthetic purposes, smooth river-run stone may be desired.
*Angular crushed stone, which will "knit" or lock together and be less likely to shift, is recommended. However, for aesthetic purposes, smooth river-run stone may be desired.
*Determine stone size by flow velocities at inlets and outlets. Typical stone for this purpose ranges between 50 mm and 250 mm. The larger the stone, the more energy dissipation.
*Determine stone size by flow velocities at inlets and outlets. Typical stone for this purpose ranges between 50 mm and 250 mm. The larger the stone, the more energy dissipation.
*Stone beds should be twice as thick as the largest stone's diameter.
*Stone beds should be twice as thick as the largest stone's diameter.
*To prevent erosion of soils beneath the stone and the migration of the stone into the soil, the stone bed should be underlain by a drainage [[Geotextiles|geotextile]].
*To prevent erosion of soils beneath the stone and the migration of the stone into the soil, the stone bed should be underlain by a drainage [[Geotextiles|geotextile]].
|-
Direct and spread flow throughout a large LID facility or to protect narrow channel sections where flow will concentrate
|Direct and spread flow throughout a large LID facility or to protect narrow channel sections where flow will concentrate
|
*While crushed stone will be less likely to shift, river-run stone may be used to create a dry-stream-bed look.
*While crushed stone will be less likely to shift, river-run stone may be used to create a dry-stream-bed look.
*The sizing of the gravel will depend on the expected velocities.
*The sizing of the gravel will depend on the expected velocities.
|}
[[Category:Materials]]
[[Category:Materials]]
[[Category:Landscaping]]
[[Category:Landscaping]]