Reviewing the Performance of Nature-Based Solutions for Stormwater Management in Urban Areas

The deployment of nature-based solutions in cities (through the creation of new green spaces) is promoted as a sustainable approach that support the stormwater management in dealing with the effects of climate change and increasing urbanization, while providing additional social, economic, and environmental benefits. These solutions operate many different ecosystem functions that regulate the urban hydrological cycle, reducing the risk of flooding and degradation of aquatic ecosystems. This study explores the performance of nature-based solutions (NbS) for managing stormwater and how it varies among diverse type of solutions. To this purpose, we conducted a literature review to extract information of the NbS functioning, runoff volume reduction rates, peak flow attenuation, and reduction of pollutant concentration. We particularly focused on the last 10 years of research in the stormwater management field considering urban forests, urban parks, street trees, green roofs, constructed wetlands, green walls, rain gardens, bioswales, and ponds. The review outcomes show that some solutions can have better performance in controlling water quality while others mainly target water quantity issues. Moreover, the effectiveness to achieve stormwater management goals is highly variable, even though considering the same type of solution. This variability can be attributed to factors intrinsic to the NbS and to characteristics of the local context. The review demonstrates the contribution that nature-based solutions (if properly designed) can have on reducing the burden on the urban drainage system. Some knowledge gaps remain in the literature regarding the design of suitable and effective solutions.