Nature-Based Solutions vs Conventional Infrastructure: Cost-benefit and Sustainability Evaluations in Built Environments

Urban areas face increasing pressure from climate change, ecological degradation, and rising infrastructure costs, prompting renewed interest in Nature-Based Solutions (NBS) as alternatives to conventional grey infrastructure. This study systematically reviews 87 peer-reviewed articles (2013–2025) to compare NBS and conventional infrastructure across economic, environmental, social, and resilience dimensions. Using a mixed-methods approach that integrates PRISMA-guided systematic review with bibliometric network analysis (VOSviewer), the study synthesizes lifecycle cost patterns, sustainability outcomes, and methodological trends. The results indicate that while NBS often involve higher initial capital investment, lifecycle cost analyses frequently report long-term savings, with median lifecycle cost differentials favouring NBS when maintenance regimes and co-benefits are included. Hydrological outcomes show consistent directional improvements, including reductions in peak discharge and runoff volume, although effect magnitudes vary significantly across climatic and design contexts. Ecological benefits are more consistently quantified than socio-cultural outcomes, revealing an imbalance in sustainability assessment frameworks. Bibliometric analysis demonstrates strong geographic concentration in high-income regions and increasing attention to governance and equity-related themes in recent years. The review identifies substantial methodological heterogeneity in cost accounting boundaries, discount-rate assumptions, monitoring duration, and indicator selection, limiting the feasibility of formal meta-analysis and constraining cross-context comparability. By integrating economic and sustainability dimensions within a single analytical structure, this study clarifies where comparative evidence converges, where it remains uncertain, and which standardization priorities are necessary to strengthen future infrastructure evaluation.