Abstract
Green roofs can be an innovative and effective way of mitigating the environmental impact of urbanization by providing several important ecosystem services. However, it is known that the performance of green roofs varies depending on the type of vegetation and, in drier climates, without resorting to irrigation, these are limited to xerophytic plant species and biocrusts. The aim of this research was therefore to compare differently vegetated green roofs planted with this type of vegetation. A particular focus was their ability to hold water during intense stormwater events and also the quality of the harvested rainwater. Six test beds with different vegetation compositions were used on the roof of a building in Lisbon. Regarding stormwater retention, the results varied depending on the composition of the vegetation and the season. As for water quality, almost all the parameters tested were higher than the Drinking Water Directive from the European Union (EU) and Word Health Organization (WHO) guidelines for drinking-water quality standards for potable water. Based on our results, biocrusts and xerophytic vegetation are a viable green roof typology for slowing runoff during stormwater events.
Highlights
IntroductionWith climate change set to intensify this trend in the future, will such episodes become more frequent, and more people will be vulnerable to them, increasing the risk of health hazards [5,9,10,11,12,13,14] and significant economic losses [9,12]
This study assessed some of those services related to the water cycle, by using small test beds to mimic green roofs with different vegetation composition and mainly using native species which are well suited to the hot and dry Mediterranean summers
Vegetation cover was low in the majority of the test beds, which is a consequence of the lack of irrigation combined with the historic climatic conditions, the results showed that they were able to act as a buffer against stormwater episodes, by storing water in the vegetation and substrate
Summary
With climate change set to intensify this trend in the future, will such episodes become more frequent, and more people will be vulnerable to them, increasing the risk of health hazards [5,9,10,11,12,13,14] and significant economic losses [9,12]. The reduction in biodiversity due to habitat fragmentation and/or degradation [15,16,17,18] and the increase in pollution levels [19,20,21] are two other major threats that can arise or be aggravated by higher population densities in urban environments
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