- Rain garden areas of about 10-20% of upstream impervious area are recommended. Optimum rain garden size is about 50 sq.m. draining 250 sq.m. of impervious area.
- Smaller, distributed rain gardens are better than single large scale facilities.
- Locate rain gardens a minimum 30.5 m from wells, 3 m downslope of building foundations, and only in areas where foundations have footing drains and are not above steep slopes.
- Provide pre-treatment and erosion control, i.e. grass filter strip to avoid introducing sediment into the garden.
- At point-source inlets, install non-erodable material, sediment cleanout basins, and weir flow spreaders.
- Bottom width - 600 mm (min.) to 3,000 mm (desirable). Length-width ratio of 2:1.
- Side slopes - 2:1 maximum, 4:1 preferred for maintenance. Maximum ponded level - 150 - 300 mm.
- Draw-down time for maximum ponded volume - 72 hours.
- Treatment soil depth - 450 mm (min.) to 1,200 mm (desirable); use soils with minimum infiltration rate of 13 mm/hr.
- Surface planting should be primarily trees, shrubs, and groundcovers, with planting designs respecting the various soil moisture conditions in the garden. Plantings may include rushes, sedges and grasses as well as lawn areas for erosion control and multiple uses.
- Apply a 50-75 mm layer of organic mulch for both erosion control and to maintain infiltration capacity.
- Install a non-erodible outlet or spillway to discharge overflow.
- Avoid utility or other crossings of the rain garden. Where utility trenches must be constructed below the garden, install trench dams to avoid infiltration water following the utility trench.
- Drain rock reservoir and perforated drain pipe may be avoided where infiltration tests by a design professional show a subsoil infiltration rate that exceeds the inflow rate.
- Allotments.
- Blue roof.
- Fountain.
- Green roof.
- Hydroponics.
- Landscape architect.
- Landscape design.
- Living facade.
- Passive water efficiency measures.
- Patio stone.
- Planting.
- Rainwater harvesting.
- Sewer construction.
- The benefits of urban trees.
- Sustainable Urban Drainage Systems.
- Water engineering.
Revision history of "Norman Fellows"
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