Policies for sustainable drainage systems in urban contexts within performance-based planning approaches

In the context of increased urban pluvial flooding risk associated with climate changes and urbanization processes there is a rising demand for a shift from storm-water management approaches that rely on conventional systems, to those aimed at mitigating the eco-hydrological impacts of urban development by the use of Sustainable Urban Drainage Systems (SUDS). Current planning approaches and policies should effectively deal with environmental challenges, especially when looking at the sustainable storm-water management. Policies for SUDS can find a fertile ground in performance-based planning which aims at achieving a set of planning objectives without imposing specific binding indications, but allowing for flexible solutions. Starting from the identification of a set of "performance-based criteria", this paper discusses different approaches concerning the adoption of SUDS in cities by examining various policy tools. Exemplifying cases of these policies application across international cities are reviewed to evaluate their prevalent performance-based character. The introduced criteria are also used to analyse criticalities, challenges and general implications about the implementation of the different kind of policies in new and existing urban developments. Results suggest that policies cannot be considered purely performance-based but rather have a hybrid character and can be implemented also under mainly conformative planning systems.