Multiple criteria-based assessment of Nature-based Solutions for flood management: A systematic review

Nature-based Solutions (NbS) offer a promising strategy for mitigating flood risks and enhancing resilience to climate change. Despite the recognised benefits of NbS, a comprehensive overview of their targeted areas, objectives, and assessment criteria remains lacking. Our systematic review fills this gap by synthesizing 132 case studies into a structured framework of 62 objectives across four domains: environmental health, social and cultural values, human well-being and livelihoods, and disaster risk reduction. This was achieved via a Multiple Criteria Decision Analysis approach inspired by value-focused thinking. Value-focused thinking allowed mapping what stakeholders aim to achieve, expressed as objectives to be either maximised or minimised. Objectives were clustered, leading to a hierarchy with categories and domains. Each objective has at least one criterion or a few criteria to measure the performance of the NbS. We found limited guidance in recommending relevant criteria according to stakeholders' needs. There are a multitude of case studies for the Global North, but much less for the Global South, though the latter is disproportionally impacted by climate change. We proposed a three-stage approach for selecting NbS alternatives, encompassing land suitability features, socio-environmental risk, and NbS benefits. The proposed hierarchical framework allows stakeholders to tailor their evaluation process to their context and objectives and navigate complex decision-making more effectively. Our findings highlight the importance of stakeholder-driven objectives and traceable assessment criteria. Moving forward, decision support tools integrating context-specific metrics can facilitate decision-making and encourage the widespread adoption of NbS initiatives.