Changes

[[File: Kenollie Rain Garden.jpeg|thumb|This rain garden in a school yard uses stone as both decorative edging and for erosion control.]]

[[File: Kenollie Rain Garden.jpeg|thumb|This rain garden in a school yard uses stone as both decorative edging and for erosion control.]]

[[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.]]

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 or gravel can serve as a low maintenance decorative feature, but it may also serve many practical functions on the surface of an LID practice.

 

Aggregates used to line [[swales]] or otherwise dissipate energy (e.g. in [[forebays]]) should have high angularity to increase the permissible shear stress applied by the flow of water. <ref>Roger T. Kilgore and George K. Cotton, (2005) Design of Roadside Channels with Flexible Linings Hydraulic Engineering Circular Number 15, Third Edition  https://www.fhwa.dot.gov/engineering/hydraulics/pubs/05114/05114.pdf</ref> However, in some surface landscaped applications there may be a desire to use a rounded aggregate such as 'river rock' for aesthetic reasons. Rounded stones should be of sufficient size to resist being moved by the flow of water. Typical stone for this purpose ranges between 50 mm and 250 mm. The larger the stone, the more energy dissipation.

*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

*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.

*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]].

[[Category:Materials]]

[[Category:Materials]]

[[Category:Landscaping]]

[[Category:Landscaping]]