The Opportunities and Challenges for Urban NBS: Lessons from Implementing the Urban Waterbuffer in Rotterdam

Abstract In Rotterdam, the proportion of impervious surfaces has increased due to urbanisation and changing land use priorities. Combined with the effects of increasingly frequent extreme rain events and longer dry periods, the current capacity of the urban water system is reaching its limits. In response to the lack of retention capacity in the neighbourhood Spangen, a hybrid Nature-based Solution (NBS) was implemented in the summer of 2018. This NBS, called the Urban Waterbuffer, has been at the heart of the Rotterdam case study, focusing on drivers and barriers for implementation, direct and indirect costs, and (co-)benefits of the system. The case study compared this hybrid approach to dealing with heavy rainfall with grey and green alternatives at a neighbourhood scale. Seven lessons were drawn on the opportunities and challenges for implementing NBS for urban water management in the Dutch context. The smaller scale of this case study, compared to other case studies in the NAIAD project, highlighted the similarities and differences in NBS effectiveness and viability across a wide range of spatial scales. The lessons learned from this Rotterdam case study can facilitate future decision-making on, and implementation of climate-adaptive urban water management strategies across Europe.