Abstract. Transportation infrastructure is crucial to the operation
of society, particularly during post-event response and recovery.
Transportation assets, such as roads and bridges, can be exposed to tsunami
impacts when near the coast. Using fragility functions in an impact
assessment identifies potential tsunami effects to inform decisions on
potential mitigation strategies. Such functions have not been available for
transportation assets exposed to tsunami hazard in the past due to limited
empirical datasets. This study provides a suite of observations on the
influence of tsunami inundation depth, road-use type, culverts, inundation
distance, debris and coastal topography. Fragility functions are developed
for roads, considering inundation depth, road-use type, and coastal
topography and, for bridges, considering only inundation depth above deck
base height. Fragility functions are developed for roads and bridges through
combined survey and remotely sensed data for the 2011 Tōhoku earthquake and
tsunami, Japan, and using post-event field survey data from the 2015 Illapel
earthquake and tsunami, Chile. The fragility functions show a trend of lower
tsunami vulnerability (through lower probabilities of reaching or exceeding
a given damage level) for road-use categories of potentially higher
construction standards. The topographic setting is also shown to affect the
vulnerability of transportation assets in a tsunami, with coastal plains
seeing higher initial vulnerability in some instances (e.g. for state roads
with up to 5 m inundation depth) but with coastal valleys (in some
locations exceeding 30 m inundation depth) seeing higher asset vulnerability
overall. This study represents the first peer-reviewed example of empirical
road and bridge fragility functions that consider a range of damage levels.
This suite of synthesised functions is applicable to a variety of exposure
and attribute types for use in global tsunami impact assessments to inform
resilience and mitigation strategies.
Tsunamis can have severe impacts on society. In addition to casualties and damage to buildings, they can also damage and disrupt critical infrastructure. To support effective risk management, it is important to understand the possible extent, severity and duration of these impacts. While impacts on buildings and casualty estimations are relatively well developed for tsunamis, critical infrastructure impact models are either not available or lack accurate vulnerability information. This paper addresses these issues by reviewing global tsunami impacts to critical infrastructure to develop a semi-quantitative tsunami damage matrix for critical infrastructure components and systems. One potential application of the damage matrix is demonstrated within an impact assessment process for Christchurch, New Zealand. The impact assessment determines asset damage likelihood for energy, water, telecommunication and transportation assets from a large tsunami inundation scenario. Consistent with observations from previous international tsunamis, above-ground assets and buried storm water pipe networks in Christchurch were found to perform poorly, while buried potable and waste water pipe networks were less impacted. This process provides a simple, but widely applicable, impact assessment approach which further studies can build on. Future research should focus on developing quantitative probabilistic tsunami vulnerability models for critical infrastructure that implement multiple asset standards and hazard intensity measures, and better account for uncertainty.
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