Adaptation measures to climate change. Integration of green roofs with rainwater harvesting systems

摘要

Nowadays it is imperative to assess the effects of climate change and develop mitigation and adaptation measures, particularly in urban environments, as cities will comprise 2/3 of the world's population by 2050, according to the UN. The use of rainwater in buildings can be a good solution to reduce flood peaks of stormwater in public areas, which may increase as a result of climate change, but also to increase water efficiency in buildings. Indeed, hydric stress is increasing on a global scale (especially in the Mediterranean basin) and it is imperative to search for measures to face these consequences. On the other hand, the use of green roofs (GR) in buildings can also bring many advantages, since it also cushions peak flows of stormwater in cities and increases the number of green infrastructures as well as all its associated benefits. Thus, it is possible to state that the GR technology combined with rainwater harvesting systems is particularly promising, pointing to the importance of developing studies that help the combined design of these systems, specifically runoff coefficients. The contributions of roofs to environmental sustainability can be further enhanced by the inclusion, for example, of photovoltaic panels, which conduces mitigation of climate change by increasing the production of renewable energy. In Portugal, a project is under development for modular roofs involving these three technologies, seeking to contribute to greater future sustainability in urban environments. The project involves research related to these different technologies and their integration, and in this paper we present the first results obtained in relation to runoff coefficients, in view of the combination of the green roof with a rainwater harvesting system in regions with a Mediterranean climate. The theoretical results show low values and wide variations in the runoff coefficients, with a minimum of 0.04 and maximum of 0.14, in terms of annual averages, which are significantly lower than the values that are usually suggested in the bibliography. Experimental tests to validate these results are in progress.