Probabilistic assessment of road accessibility under cascading hazards

Abstract

Natural hazard events such as seismic events tend to trigger cascading hazards damaging the road networks which are multi-component and widespread systems. Road accessibility is vital for response activities including emergency services by critical facilities. For disaster response and recovery planning purposes, a good understanding of hazards in the region and their impact on road accessibility is essential. To achieve this objective the study suggests a comprehensive approach to model hazards and the response of different types of assets that comprise the road network.Due to the uncertain nature of hazard events and response of road network components, a probabilistic framework is proposed to evaluate road accessibility by systematically considering the effects of: (i) multi-hazards that are cascading; and (ii) damage of various components of the network. The method tracks the uncertainty in the hazard modelling to the fragility of the road assets through a Monte Carlo simulation that creates thousands of possible road damage realizations. In each realization, the road accessibility is calculated, and accessibility probability maps for post-event response are generated from that. The method has been demonstrated for the road infrastructure of Napier City, New Zealand for a Mw8.4 Hikurangi Subduction interface earthquake. The road accessibility maps are useful resources for local authorities for resilience planning purposes. The study also presents the benefits of a few resilience intervention options in improving the accessibility of affected suburbs in the study region.