Sustainable urbanization and marine protection: A novel lifecycle approach using fuzzy-TOPSIS for green...

Green Urban Underground Spaces (GUUS) provide a promising solution to challenges of land scarcity, environmental degradation, and marine pollution in expanding cities. Nevertheless, existing studies have not established a comprehensive framework to evaluate the sustainability of GUUS with explicit consideration of their role in marine pollution mitigation. To address this gap, this study asks how GUUS alternatives can be systematically assessed to balance environmental, economic, and social sustainability while contributing to marine protection. We develop an integrated Fuzzy-TOPSIS and Lifecycle-Informed Assessment (LCA) framework that advances conventional multi-criteria decision-making approaches by incorporating uncertainty in expert judgments, evaluating lifecycle trade-offs across construction and operation phases, and directly linking underground development to marine environmental outcomes. This methodological integration enables more robust and realistic sustainability rankings compared to traditional models. The purpose of this study is to provide a decision-support framework that guides the planning and implementation of GUUS. At the same time, its main contributions lie in introducing the first lifecycle-informed fuzzy decision model tailored to underground urban infrastructure, demonstrating that multifunctional GUUS alternatives integrating stormwater management, waste control, and energy efficiency achieve higher sustainability scores than single-purpose designs, and offering policymakers and planners an actionable tool to align urban underground development with long-term sustainability and marine protection objectives. The empirical findings confirm that alternatives such as GUUS-1 and GUUS-4 outperform others in overall sustainability, whereas GUUS-5, despite its strong performance in flood control, lacks broader benefits. Sensitivity analysis further reveals that variations in environmental and economic weighting have a significant impact on rankings, underscoring the importance of balanced decision criteria.