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.