A multi-hazard risk model with cascading failure pathways for the Dawlish (UK) railway using historical and contemporary data

Keith Adams,Mohammad Heidarzadeh

doi:10.1016/j.ijdrr.2021.102082

Keith Adams, Mohammad Heidarzadeh

Open Access

https://doi.org/10.1016/j.ijdrr.2021.102082

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Abstract

The failure of the vital economic railway link between London and the southwest of the United Kingdom in the 2014 storm chain incurred up to £1.2bn of economic losses. This incident highlighted the urgent need to understand the cascading nature of multi hazards involved in storm damage. This study focuses on the Dawlish railway where a seawall breach caused two months of railway closure in 2014. We used historical and contemporary data of severe weather damage and used failure analysis to develop a multi-hazard risk model for the railway. Twenty-nine damage events caused significant line closure in the period 1846–2014. For each event, hazards were identified, the sequence of failures were deconstructed, and a flowchart for each event was formulated showing the interrelationship of multiple hazards and their potential to cascade. The most frequent damage mechanisms were identified: (I) landslide, (II) direct ballast washout, and (III) masonry damage. We developed a risk model for the railway which has five layers in the top-down order of: (a) root cause (storm); (b) force generation (debris impact, wave impact, overtopping, excess pore pressure, wind impacts); (c) common cause failure (slope instability, rail flooding, coping and parapet damage, foundation failure and masonry damage); (d) cascading failure (landslide, ballast washout, upper masonry seawall failure, loss of infill material), and (e) network failure forcing service suspension. We identified five separate failure pathways and damage mechanisms by analysing these 29 major events.

Highlights

The United Kingdom has nearly 16,000 km of open rail routes [1] with a significant proportion of coastal alignment
We study historical and contemporary data on the failure of the Dawlish railway by storm induced forces to establish a multi-hazard risk model with cascading failure pathways (FPW) which could be used with an exposure database to evaluate risk to the structural assets
This study identifies and proposes the elements of failure which may cascade across damage mechanisms (DM) and have the effect of increasing the severity of the disaster event

Summary

Introduction

The United Kingdom has nearly 16,000 km of open rail routes [1] with a significant proportion of coastal alignment. Most of these are strategically important as they often are the only regional rail connection, or they provide logistical support to critical national infrastructure. Where coastal railways are subject to direct wave action, they are vulnerable to climate change effects including sea level rise (SLR) and increases in storminess and rainfall [4]. Network Rail, the infrastructure owner in the UK, has acknowledged weather resilience and climate change as a major risk to future operations, and in response has produced a series of adaptation plans. The latest is the “Second Climate Change Adaptation Report” [9], with a third due in 2021 [10]; the organisation has contributed to the “Tomorrow's Railway and Climate Change Adaptation” research programme [11]

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