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Reservoir stone and choker layer[edit]

The highest void ratio is found in uniformly graded aggregate, as there are no smaller particles to occupy the inter-particle pores.
Higher permeability is found in larger, angular, uniformly graded aggregate. This is due to larger pore sizes and lower tortuosity.

The important characteristics of the stone within the reservoir or underdrain are the lack of fines, the void ratio and (to a lesser extent) the permeability. Porosity and permeability are directly influenced by the size, gradation and angularity of the particles [1]

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. [2] However, in some surface landscaped applications there may be a desire to use a rounded aggregate such as 'river rock' for aesthetic reasons.

Stone mulch[edit]

Stone mulch exists [3]

  1. Judge, Aaron, "Measurement of the Hydraulic Conductivity of Gravels Using a Laboratory Permeameter and Silty Sands Using Field Testing with Observation Wells" (2013). Dissertations. 746.
  2. Roger T. Kilgore and George K. Cotton, (2005) Design of Roadside Channels with Flexible Linings Hydraulic Engineering Circular Number 15, Third Edition
  3. 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