Nature-based solutions trends in urban water security: a pre-2021 retrospective look from science and practice

Introduction Extreme weather events combined with urbanization patterns have exacerbated urban flooding and drought risks, threatening water security in cities. Nature-based solutions (NbS) have emerged as a transformative paradigm to address the environmental and resultant societal challenges. This study provides a retrospective systematic look at NbS trends for hydrometeorological risks that precedes major global policy shifts post-pandemic establishing a foundational baseline.Materials and Methods The paper adopts a systematic literature review until December 2020 guided by the PRISMA protocol. Out of 468 records from the Web of Science Core Collection, 124 were finally included for review. The methodology complemented the systematic review with manual thematic inductive–deductive coding and co-occurrence analysis to examine NbS typologies, spatial, geographical and integrated socio-economic aspects.Results The analysis revealed that pre-2021 studies focused more on urban flooding than drought risk, with a greater variety of NbS implemented at neighbourhood and city levels. Higher co-occurrence of NbS was observed in urban settlements and small-to-medium-sized cities from the Global North, and large-to-mega cities from the Global South. While environmental aspects dominated NbS discourse, social and economic dimensions remained under-represented. However, co-occurrence analysis indicated significant potential for harnessing social and ecological co-benefits across multiple NbS typologies.Conclusion Integrating NbS as spatial strategies with social participation and community perspective is fundamental for enhancing its hydrological effectiveness and co-benefits. This retrospective analysis identifies a shift from theoretical recommendations to practical implementation, contextualized within relevant post-2020 literature, thereby serving as a benchmark for future research and urban water governance.