The study has taken the implementation of traditional drainage techniques (hard drainage systems into sewage systems or separate surface drainage systems) as a baseline, and compared the costs and benefits of replacing traditional systems with SUDS . An initial assessment of SUDS cost and benefits showed that permeable paving costs were less on a lifecycle basis than those of traditional surfaces and have reduced maintenance costs. Water butts provide economic benefits via savings in water costs. On the other hand, it was found that other types of SUDS such as swales and filter drains tend to show a cost-benefit ratio of less than 1, therefore implying that they cost more and provide fewer benefits. Where relevant, these systems were applied at the end-of-life of the current traditional systems or hard surfaces. The available data on surface areas for undertaking SUDS retrofitting came from the Generalised Land Use database from the Communities and Local Government of the United Kingdom .