Rocinha (Rio de Janeiro, Brazil) is the largest favela in South America. It is located on a steep mountain slope in the Tijuca National Park with a population of over 160,000 living in poor environmental, health and hygiene conditions. The geomorphological and urban setting of Rocinha makes it vulnerable to natural hazards, with the greatest risk posed by flooding or landslides, compromising the precarious balance between ecosystem services (ES) provision and human well-being. The paper aims to assess and map ES provision in a context where available data to identify areas vulnerable to natural risks is limited. The ES analyses were adapted to the specific socio-economic and environmental context of favelas, which are characterised by dense, continuously built-up environment and a high proportion of impervious surfaces, leading to deteriorating environmental, health and hygiene conditions over time. The ES-based approach was pivotal for setting out strategies-including nature-based solutions (NBS)-to mitigate disaster risk and increase local resilience. These strategies were selected taking into account the context of Rocinha and feasibility. The research shows that ES assessment can be the starting point for projects based on NBS with a view to increasing resilience even in environmentally critical contexts.Sustainability 2019, 11, 4 2 of 13 landslides, tornados, hail, and frost [2]. These disasters destroyed many buildings, causing displacements and deaths [3]. The most serious events were the 2001 floods which caused the country's worst ever natural disaster in its mountainous region, and the 2010 landslides which caused over 40 fatalities among the inhabitants of a Rio de Janeiro shantytown after a rainstorm [1,4].Nature-based solutions can increase the provision of urban ecosystem services. Solutions of this kind include green spaces (such as urban parks, gardens, forests, vacant lots and orchards) and so-called "blue infrastructure" (such as streams, lakes, water retention ponds and water springs). Ecosystem services can be defined as "the benefits that humans obtain from ecosystem functions" [5,6], or as the "direct and indirect contributions from ecosystems to human well-being" [7] that make human life possible in natural ecosystems.One of the services provided by urban ecosystems is their contribution to the water regulation cycle as rainfall capture by vegetation and permeable soils reduces the pressure on urban drainage systems and minimises the risk of flooding. Water drainage is even more critical in a context such as Rocinha, where buildings occupy 695,000 square metres, or 80% of the total area of 850,000 square metres.Adopting an ES framework can help to establish appropriate management, conservation, and renewal strategies by establishing which areas are most exposed to risk from natural disasters and the appropriate NBS for restoring them [8][9][10].Rainfall-runoff monitoring and upstream water yield forecasting modelling are essential technical processes for disaster risk management. Their asse...