From Runoff to resilience Multifunctional Nature-Based Solutions in Urban Stormwater Management: Comparative Insights from Barcelona, Boston, and Rotterdam

In response to the growing challenges posed by climate change and rapid urbanization, this research investigates the intricate dynamics of stormwater-related urban hazards. It emphasizes the risks and needs arising from environmental injustice, high-intensity rainstorm events, limited combined sewer system capacities, and the prevalence of impervious surfaces.  A cross-comparative analysis is conducted in three coastal cities—Barcelona, Boston, and Rotterdam—each with distinct climates and policy frameworks, but facing shared challenges in urban stormwater management. The study advocates for tailored Nature-Based Solutions (NBS) to address these issues while incorporating diverse perspectives to comprehensively evaluate their effectiveness.

The study underscores the urgency of integrating detailed risk assessments with strategic NBS planning to bridge the gap between current urban water management practices and the evolving needs for environmental resilience and societal well-being. A comprehensive framework is established for assessing climate-change-induced hydrological risks, implementing NBS, collecting evidence, and providing actionable guidance to decision-makers.

Adopting a Social-Ecological-Technological Systems (SETS) framework, the research explores the interactions among these interdisciplinary domains. First, it employs a novel methodology that integrates SETS vulnerability, hazard, and exposure factors into a spatially explicit risk score, offering nuanced insights into the impacts of water-related hazards on urban communities (IPCC, 2012; IPCC, 2022). Second, it develops baseline and themed NBS scenarios alongside site potential maps, presenting a systematic and replicable methodology for identifying suitable NBS implementation areas within urban environments. These scenarios account for SETS constraints, categorizing areas from fully feasible to infeasible. Third, the study evaluates the mitigation potential of NBS in reducing vulnerability while enhancing co-benefits, such as thermal comfort, recreation, water storage, habitat provision, and improved water quality.

The findings highlight the multifunctionality of NBS in complementing traditional grey infrastructure while strengthening urban resilience. By integrating natural elements, NBS delivers a wide range of ecosystem services that benefit urban populations. This study emphasizes the critical importance of flexible, forward-thinking, and equitable planning to adapt to climate change.