Changes

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 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===

===Stone for erosion control===

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.

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.

*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]].

*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.

{{:Stone: Gallery}}

File:Geogrid and geotextile.jpg

===Stone mulch===

===Stone mulch===

Stone mulch exists

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>.

<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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[[Category:Materials]]

[[Category:Materials]]

[[Category:Landscaping]]

[[Category:Landscaping]]