Generic ‘nature-based’ framing may distort understanding of the effectiveness of hydrometeorological risk reduction measures

• Coherence between ‘nature-based’ framing and the actual interventions is critical. • ‘Nature-based’ framing has a performative impact on funding landscapes. • Indicators to evaluate effectiveness of complex measures are lacking. • We suggest reporting guidelines for complex risk reduction measures. The use of natural features for hydrometeorological risk reduction has been recently promoted in international strategies and led to an increasing number of actions framed, in particular, as nature-based solutions (NbS). This has sparked a growing debate about the performative role of these concepts in shaping the funding landscape. While several frameworks have been proposed to evaluate the NbS implementation, they can only be effectively applied if NbS and evaluation indicators are clearly defined within and across the individual projects. In this article, we draw upon knowledge representation theory and we provide an evolutionary analysis of the NbS and related concepts and a review of current funding calls in Europe (n = 53) and individual projects globally (n = 342). This allows us to show how NbS have become dominant in recent practical discussions on hydrometeorological risk reduction. While terminological framing as NbS is needed to link individual projects to pre-existing knowledge, our analysis reveals that it can also tend to leverage and legitimise funding. This leads to adverse effects on expert knowledge-building especially in urban settings where hydrometeorological risk reduction necessitates complex approaches, integrating various measures. We assert that too generic NbS framing introduces additional uncertainty in assessments of NbS effectiveness and potentially excludes other viable measures from consideration and implementation. We therefore argue that coherence between the stated NbS and the indicators capturing effectiveness of actual set of measures is critical for gaining evidence from monitoring of hydrometeorological risk reduction projects. For these purposes, we propose a guideline for transparent reporting of aims, concepts, implementation outcomes, and indicators for projects aiming at hydrometeorological risk reduction. Our work highlights the need for global coherence, cross-sectoral knowledge integration, and context-sensitive evaluations to ensure that NbS deliver multiple co-benefits beyond risk reduction.