Failure mechanisms in blue-green infrastructure:

Abstract

Blue-green infrastructure (BGI) plays a significant role in the resilience of Dutch cities to the rising societal challenges and climate change effects. However, their condition is often neglected by asset managers, possibly resulting in operational failures and rapid deterioration. This research aims to identify the failure mechanisms of three commonly used BGI systems (permeable pavements, bioswales and retention ponds) during their whole life cycle. A comprehensive review of literature was conducted first, along with experts' assessment. Fault tree analysis was used to explore failure modes, degradation processes and root causes. Root causes were evaluated through minimal cut sets analysis and ranked by their criticality, propagation and impact. The findings were validated by a team of experts and structured in three fault trees accounting for 400 possible failure mechanisms: 84 for retention ponds, 115 for permeable pavements and 201 for bioswales. Clogging and hydraulic overloading emerged as key failure mechanisms in permeable pavements and bioswales, triggered by diverse root causes. Failures in retention ponds are largely linked to permanent pool conditions. The results provide a foundation for developing standardized inspection and monitoring protocols that address current gaps in the asset management of BGI.