Difference between revisions of "Stone"

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Stone or gravel can serve as a low maintenance decorative feature, but it may also serve many practical functions in an LID practice. Typical stone functions in LID and direction on selection are provided in the table below:
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[[File: Kenollie Rain Garden.jpeg|thumb|This rain garden in a school yard uses stone as both decorative edging and for erosion control.]]
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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.]]
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For advice on aggregates used in [[Underdrains|underdrains]], see [[Reservoir aggregate]].
  
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{| class="wikitable"
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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.
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| 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 purpose smooth river run stone may be desired.
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===Stone for erosion control===
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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 in diameter. The larger the stone, the more energy dissipation.
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*Stone beds should be twice as thick as the largest stone's diameter.
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*If the stone bed is underlain by a drainage [[Geotextiles|geotextile]], annual inspection and possible replacement should be performed as there is a potential for [[clogging]] of this layer to occur. 
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| *The stone sizing is based on flow velocities at inlets and outlets, but typically ranges between 50 mm and 250 mm.  
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{{:Stone: Gallery}}
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===Stone mulch===
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| *The thickness of the stone bed is twice that of the largest stone diameter.
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Finer inorganic mulch materials can be of value applied in areas with extended ponding times i.e. in the the centre of recessed, bowl shaped [[bioretention]], [[stormwater planters]], [[trenches]] or [[swale]] practices. Inorganic mulches resist movement from flowing water and do not float. Applying a thin layer of inorganic mulch over the top of wood based mulch has been shown to reduce migration of the underlying layer by around 25% <ref>Simcock, R and Dando, J. 2013. Mulch specification for stormwater bioretention devices. Prepared by Landcare Research New Zealand Ltd for Auckland Council. Auckland Council technical report, TR2013/056 </ref>.  
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Inorganic mulches which may be available locally, include:
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*Pea gravel
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*River rock/beach stone
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| *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 geotextile."
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*Recycled glass
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*Crushed mussel shells
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| 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.
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[[Category:Materials]]
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[[Category:Landscaping]]
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| *The sizing of the gravel will depend on the expected velocities."
 
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Latest revision as of 15:05, 15 July 2020

This rain garden in a school yard uses stone as both decorative edging and for erosion control.
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, see Reservoir aggregate.

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.

Stone for erosion control[edit]

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. [1] 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 in diameter. The larger the stone, the more energy dissipation.

  • Stone beds should be twice as thick as the largest stone's diameter.
  • If the stone bed is underlain by a drainage geotextile, annual inspection and possible replacement should be performed as there is a potential for clogging of this layer to occur.

Stone mulch[edit]

Finer inorganic mulch materials can be of value applied in areas with extended ponding times i.e. in the the centre of recessed, bowl shaped bioretention, stormwater planters, trenches or swale practices. Inorganic mulches resist movement from flowing water and do not float. Applying a thin layer of inorganic mulch over the top of wood based mulch has been shown to reduce migration of the underlying layer by around 25% [2]. Inorganic mulches which may be available locally, include:

  • Pea gravel
  • River rock/beach stone
  • Recycled glass
  • Crushed mussel shells
  1. ↑ 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
  2. ↑ Simcock, R and Dando, J. 2013. Mulch specification for stormwater bioretention devices. Prepared by Landcare Research New Zealand Ltd for Auckland Council. Auckland Council technical report, TR2013/056

A lot level bioretention cell designed to receive and detain, infiltrate and filter runoff, typically used for discharge from downspouts.

Includes the protection of soil from dislocation by water, wind or other agents.

Linear bioretention cell designed to convey, treat and attenuate stormwater runoff. The engineered filter media soil mixture and vegetation slows the runoff water to allow sedimentation, filtration through the root zone, evapotranspiration, and infiltration into the underlying native soil.

A shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades.

(1) The wearing away of the land surface by moving water, wind, ice or other geological agents, including such processes as gravitation creep; (2) Detachment and movement of soil or rock fragments by water, wind, ice or gravity (i.e. Accelerated, geological, gully, natural, rill, sheet, splash, or impact, etc).

A broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations.

Low Impact Development. A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

A broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations.

A broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations.

a top dressing over vegetation beds that provides suppresses weeds and helps retain soil moisture in bioretention cells, stormwater planters and dry swales.

a top dressing over vegetation beds that provides suppresses weeds and helps retain soil moisture in bioretention cells, stormwater planters and dry swales.

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.

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