Changes

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. 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]], regular inspection and possible replacement should be scheduled as there is a potential for [[clogging]] of this layer to occur.

{{:Stone: Gallery}}

File:Geogrid and geotextile.jpg|Coarse angular stone laid onto a geogrid and geotextile. Image from wikimedia commons

===Stone mulch===

===Stone mulch===

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 inrgonaic 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>.  

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>.  

Inorganic mulches which may be available locally, include:

Inorganic mulches which may be available locally, include:

*Crushed glass

*Crushed glass