Source control overview

The inclusion of source control in SuDS schemes is one of the more important principles of SuDS design and source control components should be upstream of any pond, wetland or other SuDS component. Source control can help provide interception storage which can handle and treat some of the more frequent but smaller, polluting events (at least 5mm, if not 10mm)

Most source control components will be located within the private properties or highway areas. Their purpose is to manage rainfall close to where it falls, not allowing it to become a problem elsewhere. The main type of source control covered here include:

• Green roofs

• Rainwater harvesting

• Permeable paving

• Other permeable surfaces

Source controls look to maximise permeability within a site to promote attenuation, treatment and infiltration reducing the need for offsite conveyance. Green roofs (figure 1) achieve this increasing the amount of ground and vegetation cover on roofs, which increases storage, attenuation and evapotranspiration helping manage flows as well as providing other benefits like thermal comfort, biodiversity etc.

Permeable paving (figure 2) allows water to soak into the gravel sub-base below, temporarily holding the water before it soaks into the ground, or passes to an outfall (during this process there is also some water quality treatment). Rainwater harvesting systems provides opportunities to collect, temporarily store and use surface water on site.

Other features such as filter strips, soakaways, geocellular drainage, swales (particularly along highways or roads) and rain gardens can also be used as source control.

Benefits

Green roofs	Rainwater harvesting	Permeable pavements	Other permeable surfaces

Key