Maintenance matters: Insights from guidelines and practice on nature-based stormwater solutions

Nature-based stormwater solutions (NBSS) support urban stormwater management while providing additional ecosystem services. Their hybrid grey-green design sets them apart from conventional drainage systems requiring specific maintenance to ensure long-term performance. This study combines a global practitioner survey and a review of maintenance guidelines aiming to characterize shortcomings in NBSS management, focusing on failure mechanisms and maintenance practices. Based on 22 responses, survey results show that, in the absence of maintenance, systems are mainly affected by sediment buildup, litter, and green waste accumulation, as well as excessive vegetation growth, and invasive species. Maintenance (e.g., visual inspections, litter removal) is performed regularly, from monthly to annually, consistent with guidelines. Vegetation management typically follows a seasonal frequency (∼three months). Our review of 35 guidelines indicates that maintenance practices are very diverse and context-dependent, depending on the type of NBSS and socio-ecological-technological context, reflecting a potential barrier to mainstreaming of best practices. No universal maintenance frequency can be established as it strongly depends on NBBS and local context (e.g., climate, available resources). Systematic data collection on failures, their occurrence, and impacts is however essential to support predictive local maintenance strategy.