Difference between revisions of "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 [[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]]. | ||
{{:Stone: Gallery}} | |||
===Stone mulch=== | ===Stone mulch=== | ||
Revision as of 14:32, 17 March 2018
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. The larger the stone, the more energy dissipation.
- 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 geotextile.
Stone lining the ponding zone of this rain garden. Image credit California Native Plant Society
Coarse angular stone laid onto a geogrid and geotextile. Image from wikimedia commons
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 inrgonaic 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:
- Crushed glass
- Crushed mussel shells
- Pea gravel
- ↑ 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
- ↑ 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