A multi-level framework for climate adaptation of critical infrastructure: flood risk in railway networks.

Abstract

Infrastructure systems are threatened by extreme weather events, such as river flooding. Climate change increases the frequency and severity of flooding, resulting in more repairs and operational disruptions. While this explains a clear need to adapt to changing hazards, it is often difficult to compare all adaptation options that infrastructure can benefit from in a coherent way. Objective. The aim of this paper is to propose a four-level framework for infrastructure adaptation, from asset- to system-level, and demonstrate its application in a case study of railway adaptation to flooding. Method. We apply a framework to appraise adaptation options against flooding at hazard-, asset-, network-, and system-levels in the case of a railway line in Rhineland–Palatinate, Germany. Results. Baseline flood risk for railways in Rhineland–Palatinate is €102 million yr⁻¹ (mean), with indirect losses accounting for 53% of total risk. Climate change could increase this risk by up to 310% by 2120. About 38% of the rail network length can be partly flooded, compared to a 17% Germany-wide average. None of the adaptation options were economically efficient under all scenarios (BCR > 1), but efficiency varied by location: floodwalls (L1) reached benefit-to-cost ratio (BCR) 0.88 in one area, while new network connections (L3) reached BCR 1.08 in another. Conclusion. Accounting for both flood damages and losses arising from network disruptions is essential for appraising flood adaptation options for railways. Adaptation effectiveness and economic efficiency are highly location-specific. Measures that reduce indirect losses, such as network redundancies, can outperform asset-level measures in some contexts. No single option is robust across all scenarios, highlighting the value of multi-level strategies and location-tailored planning.

Published 2 July 2026.