Are water-related Nature-based Solutions (NbS) assessed to their full multi-benefit potential? A systematic literature review.

Nature-based Solutions (NbS) leverage and mimic natural processes to address societal and environmental challenges. In recent years, they have attracted global interest for their significant contributions to the Sustainable Development Goals, offering integrated approaches to address multiple dimensions of resilience and sustainability in the context of global change. This potential is particularly promising in complex and rapidly evolving urban environments, where water resources represent both managing hazards and protecting resources. However, assessing and quantifying the full potential and impacts of NbS remains challenging, as their impacts span multiple disciplines and depend on local socio-geographical contexts and initial implementation goals. Holistic assessment frameworks are urgently required[ES1] to demonstrate performance, capture the diverse effects of NbS along the process-impact chain, and enable stakeholders to monitor progress over time. This study presents a systematic literature review to map the current state of the art in NbS performance evaluation. 111 articles were reviewed to assess whether NbS evaluation methods associated with urban water resources provide holistic and transferable approaches while addressing the complexity of human-natural systems. Preliminary results indicate that most studies focused on existing sites where NbS were considered for implementation, often using modeling approaches. Performance evaluations spanned 16 parameter categories, with the majority addressing quantitative and qualitative hydrological aspects, consistent with the authors’ disciplinary backgrounds. Although many methods demonstrated reusability and supported decision-making processes, most studies assessed limited parameters, partly due to modeling assumptions. Notably, social aspects were frequently acknowledged, particularly regarding the involvement of local governments during the implementation phase. The results of this literature review can support scientists in developing robust assessment frameworks and provide stakeholders with a comprehensive overview of the current state of the art in NbS multi-benefit characterization. This, in turn, will provide stakeholders with greater confidence to invest in NbS, upscale their use, and influence NbS policies.