Vulnerability of terrestrial transportation lines to natural events

Our modern society relies on well-functioning transport systems providing mobility, transport safety and regularity. Maintaining the operational state of roads and railways during extreme weather events or other natural events is an important and demanding task. Natural events may cause damage to transportation assets, which can immediately or over time result in functional loss of a transportation line. For instance, a reduced culvert capacity due to debris deposition and clogging, could cause flooding of a road/rail. Some natural events can lead directly to loss of service, even without damaging an asset, like the occurrence of avalanches on a transportation line, blocking the related traffic. To reduce risks of failures posed by natural hazards, it is essential to assess vulnerability of transportation networks to such events.

A well-established way to analyse vulnerability is to use damage-, loss- or fragility functions. Such functions can express both functional vulnerability, representing the functional loss for a transportation line, and structural vulnerability representing damage degree or the exceedance probability of damage levels pertinent to a transportation asset. These functions can all be expressed in terms of event intensity, which is a parameter characterizing the damaging potential of a natural event.

In order to analyse functional vulnerability, various asset types with their interdependencies i.e. network topology and geographical coincidence must be considered. Here, the applied damage and fragility functions for evaluating structural vulnerability must account for location specific data on assets and asset properties. The review of existing damage-, loss- and fragility functions showed that these are not sufficient for intended analysis and need to be updated to consider various natural events and related failure modes. Recommendations are provided on how to elaborate new damage-, loss- and fragility functions to overcome a large number of uncertainties related to impacts of natural events on infrastructure and account for resistance of infrastructure. These recommendations concern both the choice of intensity parameters for different types of hazards and definition of possible failure modes, the methods for developing the functions and the assessment of the relationship between structural vulnerability of the asset and functional vulnerability.

The research leading to these and future results receives funding from the European Community’s H2020 Programme MG-7-1-2017 Resilience to extreme (natural and man-made) events, under Grant Agreement number: 769255 - "GIS-based infrastructure management system for optimized response to extreme events of terrestrial transport networks (SAFEWAY)".