Urban floods can threaten citizens’ quality of life, produce socioeconomic losses, and act as an urban degradation driver. Restoring urban rivers, however, is not simple and its results are usually limited. It would be desirable to enhance urban fluvial systems, control flood risks, and increase city resilience while improving the city itself. This work suggests that river restoration, when applied to an urban watershed, should be supported by sustainable urban drainage measures to compensate for the negative effects induced by city growth in the water cycle, in a systemic approach to the entire watershed. A methodological framework is proposed to verify this hypothesis intending to assess urban flooding projects in a wide sense. This framework uses a hydrodynamic mathematical model and a set of multicriteria indices. A case study in Dona Eugênia Watershed, in Brazil, was developed. Two different design concepts were considered: the usual drainage design and the river restoration combined with sustainable urban drainage. Both solutions were designed to completely solve the problems, leading to virtually zero flooding in the present situation; however, environmental and urban gains were greater when using the proposed combination. Besides, when testing resilience behavior, it was also shown to be more consistent over time.

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The use of dual-drainage models has increased in recent decades, mostly because of advances in mathematical methods and geographic information system tools. This type of modelling provides precise diagnoses and can be applied to evaluate stormwater infrastructure and diverse drainage alternatives. Minor and major drainage relations in the Dona Eugênia watershed, Brazil, were analysed in this study. Three alternatives simulated the quasi-two-dimensional hydrodynamic model Modcel. The first alternative considered only the terrain surface layer, representing the current situation. In the second alternative, a layer containing a designed storm sewer was introduced. Considering the previous alternatives as a way to diagnose the main minor and major deficiencies, a third alternative was formulated considering previous projects to solve floods in the watershed, incorporating them in the second alternative with functional minor drainage. The results identified the locations of minor drainage gaps, thus helping to direct efforts to the most critical regions, optimise operations and minimise maintenance costs. The results could also be used to evaluate the effects of storm sewer network discharges in major drainage systems, leading to better design of the drainage infrastructure. The major drainage itself can be optimised, once its responsibility in flooding is identified.