Evaluating Green Roof Retrofitting as a Stormwater Management Strategy in a Brazilian Urban Watershed

Abstract

Urban flooding, driven by climate change and the expansion of effective impervious areas (EIA), poses growing challenges for sustainable urban development. Among nature-based solutions, green roofs (GRs) have gained attention for their potential to reduce surface runoff, promote infiltration, and restore aspects of the urban hydrological cycle. However, in Brazil, the adoption of GRs remains limited due to regulatory gaps and a lack of basin-scale impact studies. This research investigates the hydrological effects of GR retrofitting in a representative urban watershed in São José dos Campos, Brazil, through scenario-based modeling using the CAbc hydrological software. Scenarios were developed based on local policy frameworks, simulating varying degrees of GR implementation. The results suggest that GRs can enhance stormwater management by reducing runoff and delaying peak flows, especially under frequent, moderate rainfall events. Nonetheless, their performance tends to diminish during high-intensity storms, indicating the need for integration with other drainage strategies. The study highlights the value of GRs as part of a broader sustainable urban drainage system and supports the development of policies that incentivize their use to improve resilience in rapidly urbanizing regions.