Stone

For advice on aggregates used in underdrains, see Gravel

Stone 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 below:

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.
• The stone sizing is based on flow velocities at inlets and outlets, but typically ranges between 50 mm and 250 mm.
• The thickness of the stone bed is twice that of the largest stone 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.

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.
• The sizing of the gravel will depend on the expected velocities.

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.

Filter fabric that is installed to separate dissimilar soils and provide runoff filtration and contaminant removal benefits while maintaining a suitable rate of flow; may be used to prevent fine-textured soil from entering a coarse granular bed, or to prevent coarse granular from being compressed into underlying finer-textured soils.