Filter Strip & Swales
Content Table
Overview
One of underlying principles of SUDS is to use devices inspired by natural systems. Sloping vegetated areas are a good example of this concept. These can be a strip of ground that the water runs across (a “filter strip”) or a broad, shallow channel (a “swale”) that the water runs along when it has been raining. Filter drains are a type of source control (control of runoff or pollution a, or near, its source), whereas swales are both a source control and a means of conveying runoff away from the area being drained. Normally both devices will be dry.
As the runoff flows across the surface it is filtered by the vegetation. This traps silt and other solid contaminants. Organic content can also be reduced because micro-organisms in the soil and on the plants themselves act on the pollutants. The US EPA estimate swales can reduce suspended solids by up to 81% and heavy metals by more than 50%. Swales also act indirectly to improve water quality; using a swale instead of a surface water drain reduces the chance of misconnections. The design approach is covered in CIRIA Report C609 and the SUDS Manual (see links ) .
Schematic Diagram
Heriot-Watt University Swale
Related Articles
Article 1
Article 2
Article 3
References
Wilson, S., Bray, R., Cooper, P. (2004), Sustainable drainage systems. Hydraulic, structural and water quality advice (C609), CIRA, UK, ISBN: 0-86017-609-6 .
