Urban stormwater management (USWM) in developed countries is undergoing a significant evolution. Centralized systems are giving place to distributed facilities, mainly to cope with flooding caused by fast urban growth and with water bodies' quality degradation. This evolution has to face inertias from existing structures, but it relies on the idea that new strategies are more sustainable than old ones. We assume that USWM is strongly dependent on local conditions and objectives, and thus its sustainability has to be evaluated at a local scale. Although no global solution can be found, it is worth defining a general method to assess if an USWM strategy is sustainable on a specific site. In this paper we propose and discuss a methodology of this kind, mainly based on hydrological models. The methodology is made of three phases: definition of sustainability; modelling and analysis of several case studies; generalization procedure.