Vegetated roofs rainwater management experimental research in Brazil: A georeferenced exhaustive review of a continental-size country

Flood risk is an increasing concern in densely populated cities as urban drainage systems are demanded progressively more. The need for decentralising water management becomes relevant, and vegetated roofs are internationally known to be able to assist in locally retaining and detaining stormwater. For these Nature-based Solutions to be effective, there must be science-based standardisation, supporting decision-makers towards effective public policy-making based on hydrological performance. However, this performance should be associated with local environmental conditions, and continental-size countries such as Brazil can have a large variety of climates. At the same time, Brazil lacks a comprehensive review associating experimental results with climatic classifications. In this sense, the present work aims at reviewing the experimental research undertaken in Brazil and synthesising its rainwater retention outcomes associating it to the Köppen-Geiger climate classification. To accomplish this task, the Rational Method is used to extract and conform data from 34 records involving internationally and nationally published works as well as grey literature. Results of this work present to national researchers not only gaps but important trends, generating further innovative opportunities for work, and present to international researchers an accessible and georeferenced bulk of data on vegetated roofs' hydrological performance in Brazil with the highest possible resolution. It was found that semi-arid climates had the best average rainwater retention rates (0.79), followed by subtropical (0.54–0.72), and the tropical climates had the lowest (0.55–0.69). The work concludes that vegetated roofs have a positive hydrological performance throughout Brazil. However, further work is needed to quantify the hydrological influence of a range of different structural and environmental factors that modify the roofs' performance. It is also shown that climates, particularly outside the financial centres of Brazil, lack data and hence need further investigation and experimental research.