Green Roofs as an Urban NbS Strategy for Rainwater Retention: Influencing Factors—A Review

Abstract

There has been a rapid development in studies of nature-based solutions (NbS) worldwide, which reveals the potential of this type of solution and the high level of interest in its implementation to improve the resilience of cities. Much relevant information and many important results are being published, and it is now possible to see their diverse benefits and complexity. Several authors highlight their role in urban areas not just in temperature control, but also in human health, ecosystem development and water management. However, in the current reality of cities, where water use is being (and will be) constantly challenged, analyzing NbS advantages for the urban water cycle is crucial. This study performed an intense review of the NbS literature from 2000 to 2021, to identify their contributions to the improvement of urban water cycle management and thus provide a solid information base for distinct entities (public institutions, private investors and the urban population in general) to disseminate, apply and justify their implementation. In general terms, the urban water cycle embraces not only the abstraction of water for urban consumption, but also its return to nature and all the stages in between, including water reuse and stormwater management. This review will highlight the important benefits that NbS in general, and green roofs in particular, provide to urban stormwater control, a key factor that contributes to urban sustainability and resilience in order to face future climate challenges. The novelty of the present review paper falls within the conclusions regarding the crucial role that NbS develop in urban water management and the main features that must be tested and technically enhanced to improve their functioning.