Exploring the feasibility of implementing sustainable drainage systems (SuDS) under real-world urban conditions

Sustainable Drainage Systems (SuDS) have been widely recognized as promising approaches to mitigate environmental impacts while delivering multiple co-benefits; however, their implementation at the district or city scale remains sporadic and unsystematic, revealing a persistent gap between the theoretical potential of SuDS and their practical application. The primary objective of this PhD research is to develop and test an urban structure-driven methodology for assessing the feasibility of implementing SuDS under real-world urban conditions. The study adopts an urban analysis-based framework, conceptualizing the city as a multilayered system composed of two hierarchical domains—the roof-level domain and the ground-level domain. Within this framework, different SuDS types are classified, evaluated, and spatially mapped to analyze their technical feasibility, functional suitability, and contextual adaptability. The proposed methodology was empirically applied to three representative urban areas in Bologna, Italy, characterized by high-, medium-, and low-density urban patterns. The study quantified the proportion of transformable urban surfaces, developed an applicability matrix, and tested various design scenarios to evaluate their hydrological performance, particularly in terms of water retention capacity and spatial integration potential. The findings indicate that: (1) the transformation potential of urban surfaces varies significantly across different density patterns; (2) urban morphology plays a decisive role in determining the prioritization of SuDS interventions; and (3) improvements in water retention capacity are positively correlated with the proportion of urban surfaces transformed through SuDS measures. The main outcome of this research is a decision-support tool that assists potential stakeholders, including policymakers, urban planners, architects, and designers, in the early stages of SuDS-oriented urban refurbishment, requalification, and regeneration. By identifying a critical balance between what is needed and what is realistically achievable, this tool enhances urban rainwater management and contributes to the development of more sustainable and resilient urban environments.