Towards nature-positive engineering: nature-based solutions in attenuating coastal hydrometeorological hazards

Abstract Coastal and deltaic regions are highly vulnerable to hydrometeorological hazards such as storms, flooding, and extreme temperatures—risks that are intensifying under climate change. While hard engineering structures (e.g. levees, seawalls) remain widely used, they can be costly, ecologically disruptive, and may exacerbate hazard complexity. Nature-based solutions (NbS), including mangroves, salt marshes, and other coastal ecosystems, offer sustainable and often cost-effective alternatives or complementarities that can mitigate hazards while delivering ecological and societal co-benefits. However, their effectiveness is difficult to assess due to diverse methodological approaches, site-specific coastal dynamics, and inconsistent reporting indicators. This study synthesises the scientific evidence base on the effectiveness of NbS in reducing hydrometeorological hazards in coastal and deltaic environments and evaluates the robustness of methods used to assess their performance. A systematic review and meta-analysis of 383 peer-reviewed English-language articles published between 2008 and 2024 was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocols and the PICO framework. Using an evaluation approach adapted from the Intergovernmental Panel on Climate Change, each study was assessed for evidence robustness, level of agreement, and overall confidence. The meta-analysis provides quantitative estimates of NbS effectiveness and highlights substantial uncertainties arising from ecological variability, methodological inconsistencies, and heterogeneity in hazard indicators (e.g. wave height, flow velocity, water level, temperature) and measurement units. Findings show that NbS effectiveness is highly context dependent and influenced by site characteristics, ecological dimensions, system configuration, and hazard intensity. The study emphasises the need for standardised, hazard-specific indicators and greater use of integrated methodological approaches to strengthen the reliability and comparability of future assessments. It also identifies opportunities for advancing hybrid or nature-positive engineering solutions that combine NbS with conventional infrastructure to enhance coastal resilience.