The effects of climate change, taken along with the continuing expansion in development and urbanisation, are known to result in significant increases in surface water runoff. Often this is contaminated by environmentally damaging pollutants such as suspended solids, heavy metals, hydrocarbons and chemicals. These surface water runoff quantity and quality issues cannot be properly and effectively dealt with by conventional piped drainage systems.

Ideally, alternative drainage systems, which can improve water runoff quality and reduce or control water runoff flows to prevent flooding and stream bank erosion, are required. Sustainable drainage systems (SUDS), which correctly incorporate best management practice (BMP) techniques, can provide both water quality treatment and water quantity control along with a significant degree of amenity value, depending on the BMP technique or combination of techniques employed.

Properly designed SUDS utilising source, site and/or regional treatment control facilities and techniques (as outlined in the CIRIA SUDS Design Manuals for England, Scotland and Northern Ireland) should therefore significantly reduce detrimental environmental impacts and flooding resulting from surface water runoff in urban developments.