Cost-benefit analysis of sustainable drainage systems considering ecosystems services benefits: case study of canal do mangue watershed in Rio de Janeiro city, Brazil

The increasing demands of humankind contribute to the scarcity of natural resources and foster climate changes. For this reason, sustainable development has become a fundamental agenda in the twenty-first century. The intense urbanization induces significant changes in the natural water cycle, and this feature, coupled with neglecting the natural water dynamics in the urban planning process, increases the population’s vulnerability to urban floods. In this context, sustainable urban drainage techniques have been proposed to match the urban and natural demands, while preserving or recovering the environmental functions, as much as possible. However, such techniques are often not adopted, even in developed cities, and this fact seems to be related to the improper awareness of the whole set of benefits involved in their use. This article aims to evaluate the economic viability of sustainable urban drainage systems, in a simple and easily acceptable way, considering the ecosystem services provided by green roofs and rainwater harvesting barrels, and including their action in delivering urban revitalization and valorization. The proposed method can be easily used and understood by decision-makers, facilitating its diffusion and use in urban policy-making process. The results showed a best-performing scenario for the rainwater harvesting system with a payback of approximately three years, a benefit-cost ratio of four, and an internal return rate of 45%. The ecosystem service benefits represent 36.3% to 50.8% of total benefits.