Sustainable drainage systems (SuDS)

Urban flooding from sewers and intense rainfall is, increasingly, a threat to cities across the globe, as a result of rapid urbanisation and extreme weather. Urban surface-water flood risks are caused by inadequate drainage or space to manage runoff. Old piped drainage networks often do not have the capacity to cater for either current levels of urbanisation or climate-change impacts on rainfall intensities. The cost and feasibility of upgrading extensive infrastructure is generally prohibitive so alternative, more resilient, solutions are required. Managing stormwater runoff using SuDS delivers a more sustainable approach, providing more resilient flood risk management, natural pollution mitigation and water resource support. Without a regular supply of water, urban blue-green infrastructure (BGI) systems will be at risk of ‘drought’ and their amenity, climate resilience and biodiversity benefits will be eroded.  Nowadays, SuDS are recognised as a valuable and significant urban water resource, necessary to support and enhance the social and ecological health of our towns and cities.  The location, type and scale of components must reflect benefits available from using surface-water runoff as a resource.  Earlier sections in the chapter deal with the principles behind the development of integrated planning and design. The later sections cover approaches on SuDS used in different construction contexts and settings. The section does not reproduce detailed planning and design processes set out in other documents, such as CIRIA’s SuDS Manual.