Retrofit SUDS


Research group and website contact:
Virginia Stovin



The Retrofit SUDS Research Group aims to develop methodologies and case studies to support the broader use of SUDS retrofit to tackle a range of urban stormwater management problems. We believe that there are many opportunities within the UK's urban areas to address flooding, unsatisfactory river quality and poor urban habitats and amenity through the use of more sustainable, cost-effective, source-based storm drainage systems. Retrofitting may entail the disconnection of roof drainage from the sewer system, or the augmentation of an existing system with additional SUDS components.

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Our work includes the development of decision-support tools to assist in the selection and implementation of appropriate retrofit SUDS schemes.

We are now working with the Water Industry, the Environmental Regulators and local authorities to implement retrofit SUDS in a number of case study locations, and our research activities increasingly recognise the need to address planning and legislative issues alongside the engineering aspects.

This website provides an overview of our past and ongoing research, lists relevant publications, and also includes links to some key SUDS websites and to two reviews focusing specifically on retrofit studies in both the UK and Internationally.


Sustainable Urban Drainage Systems (SUDS) is a generic term that refers to various measures aimed at controlling surface water runoff (and consequent flooding and pollution problems) from urban catchments. SUDS may be 'non-structural' or 'structural'. Non-structural SUDS include the use of education and/or incentives to modify human behaviour. Structural SUDS include green roofs, soakaways, swales, infiltration trenches and balancing ponds. Because of their reliance on natural catchment processes, these technologies are viewed by many to constitute a 'more sustainable' approach to the management of urban storm runoff than conventional underground pipe and storage-based solutions.

To date almost all SUDS implementations in the UK have been associated with new developments. The term retrofit is employed when SUDS-type approaches are intended to replace and/or augment an existing drainage system in a developed catchment. Examples of retrofit SUDS might be the installation of green roofs, the diversion of roof drainage from a combined sewer system into a garden soakaway, or the conveyance of road runoff via roadside swales into a pond sited in an area of open space. Such measures are alternative ways of alleviating downstream water quantity and quality problems, potentially providing more effective and sustainable solutions overall.

Retrofit SUDS may be relevant in any situation where inappropriate stormwater management leads to poor performance of the urban drainage system. This includes problems associated with excessive CSO discharges, separate storm sewer outfalls and flooding of urban watercourses.