Mapping the impact: external factors and their role in green infrastructure failures for smarter maintenance planning

Graphical abstract illustrating external stressors affecting a bioretention system—including sediments, heavy metals, leaf litter, trash, and winter maintenance—and showing Trondheim hotspot maps generated with grid-based and district-based approaches, with index intensity ranging from minimal to severe and an example site highlighted on an aerial image. Effective maintenance planning for green infrastructure (GI) is constrained by limited access to data including the external factors that drive maintenance needs. This lack of information makes it difficult to estimate the appropriate frequency and type of maintenance required for specific GI types and locations. This study proposes a novel proxy-based approach which quantitatively estimates GI maintenance needs by integrating spatial datasets that represent key maintenance stressors, including leaf litter deposition, sediment and trash accumulation, winter road treatment, and heavy metal loading. The framework is demonstrated for the city of Trondheim, Norway, where the combined proxy maps provide location-specific insights to support maintenance strategies for existing GIs as well as planning considerations for future installations. Two aggregation methods – a grid-based and a district-based approach – are evaluated. The grid-based method effectively identifies localized maintenance hotspots, while the district-based approach offers broader strategic value for urban planning and prioritization. The method is flexible, generalizable, and adaptable to locally available proxy data. Future work should focus on validating proxy-based assessments through repeated field inspections to refine and calibrate the framework for accurate, decision-relevant maintenance planning.