Climate Non-Stationarity and Transport Infrastructure Vulnerability: Lessons Learned from the September 2024 Flood in Southwestern Poland

Floods are among the most destructive natural hazards affecting transport infrastructure, causing extensive damage to roads, railways, bridges, and critical transport corridors. Although numerous studies have examined the hydrological characteristics and economic consequences of flood events, relatively few have proposed integrated engineering indicators that combine flood intensity with the resulting disruption to transport infrastructure. This study presents a new analytical methodology based on the Transport Infrastructure Impact Index (TIII), developed to provide a quantitative and reproducible assessment of impacts on transport systems. The proposed methodology integrates three hydrometeorological variables (maximum precipitation, flooded area, and flood duration) with four infrastructure-related variables (affected road infrastructure, affected railway infrastructure, damaged transport bridges, and major closures of transport corridors). Following min–max normalization, these variables are combined into two analytical components: the event intensity factor (E) and the Infrastructure Disruption Factor (D), which together determine the final value of the TIII. The methodology was validated using four major flood events that occurred in Poland in 1997, 2010, 2020, and 2024. Additionally, detailed case studies of damage to the transport infrastructure were conducted for the Lower Silesia region (Dolnośląskie), one of the areas most severely affected by recent floods. The calculated TIII values (0.931, 0.304, 0.000, and 0.429, respectively) reflected the documented severity of the analyzed flood events and represented their relative impact on transport infrastructure. The proposed TIII provides a transparent, dimensionless, and easily reproducible engineering indicator for the relative comparison of flood events using routinely available hydrological and infrastructure data. The methodology can support post-disaster assessment, infrastructure resilience evaluation, the prioritization of reconstruction activities, and climate change adaptation planning. Due to its modular structure and reliance on commonly reported engineering parameters, the proposed framework can also be adapted for application in other geographical regions and utilized to assess the impacts of additional natural hazards affecting transport infrastructure.