Sustainable Drainage Systems

In urban areas, most surfaces are sealed or have been paved over, which makes it much harder for water to infiltrate or naturally soak away. In case of heavy rainfall, nearly all our rainwater goes down the drain leading to a release of dirty water into rivers.

Two different drainage systems can be distinguished:

  • In a combined system: the rainwater is taken to a sewage treatment plant which may cause the sewage treatment plant to overflow resulting in the discharge of untreated sewage into our rivers.
  • In a separate system, the rainwater goes into a pipe taking road pollution with it, which is then taken out to a nearby waterway.

Futhermore, when rain washes off our roads it takes road pollution with it; road run-off contains oils and heavy metals from our cars, and our sewage waste is full of river harming chemicals and sewage related litter.


(c) British Geological Survey |

How do SuDS work?
Sustainable drainage systems use a sequence of techniques (source control, pre-treatment, retention and infiltration) to manage the amount of rainwater entering our sewers. SuDs are considered to be environmentally beneficial due to a minimal or no long-term detrimental environmental damage. 

SuDS are more sustainable than traditional drainage models. It creates the opportunity to manage water naturally, control the speed of runoff water, reduce pollutants and create a habitat for wildlife.

Sustainable drainage is thus moving away from the traditional thinking of designing.  Through this system, flow velocity is controlled, the risk of street level flooding (water quantity) is reduced and pollutants are removed (water quality). Surface water runoff is managed for maximum benefit.

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