Samenvatting

Hard coastal defences along the Dutch–Belgian North Sea coast are nearing the end of their design life and carry significant ecological costs. Salt marsh Nature-Based Solutions (NbS) provide a self-sustaining alternative. However, existing asset-management (AM) standards continue to view them as "nice-to-have" side benefits rather than formal infrastructure components. This thesis examines how living salt marsh systems can be integrated into existing AM frameworks and assessed alongside traditional grey infrastructure.

Focusing on the Western Scheldt Zwin pilot, the research develops six performance indicators. These indicators are assessed using satellite imagery and long-term monitoring data (2016–2025) from the MANABAS coast partners. Then, three AM tools are used to assess the salt marsh. First, the risk scoring table identifies the main failure modes specific to the KPI and gives them a score of impact based on the threshold. Then, a risk matrix links each KPI to a risk class by combining the impact (from negligible to catastrophic) with the estimated time to failure (from more than 100 years to less than 1 year), assigning each case a color-coded criticality level. The same criticality score is then used for the RAMSHEEP framework, allowing managers to identify which impact categories are most at risk at each timeframe examined. And finally, an FMECA provides an overview of the most critical failure modes for streamlined prioritization of maintenance.

The research asserts that salt marshes can indeed be managed as dynamic assets if KPI monitoring, risk scoring, and maintenance interventions are aligned with ISO 55000 principles. This demonstrates how existing AM tools can be adapted to NbS while also highlighting critical gaps, particularly in cross-border monitoring and risk assessment, that must be resolved to enable broader integration of NbS into traditional AM systems.