Vulnerability of road bridge infrastructure under extreme flood events

Vulnerability of road bridge infrastructure under extreme flood events

Road network and critical road structures such as bridges, culverts and floodways have a vital role before, during and after extreme events to reduce the vulnerability of the community being served. Understanding the resilience of existing structures to known natural hazards empowers the road authorities in risk mitigation and emergency management. Major resources available to researchers to address the complex problem are the recent case studies of extreme events where failures of infrastructure and resultant impact on community have been captured by some road authorities. For example, 2010-2011 floods in Queensland in Australia had a huge impact particularly on central and southern Queensland resulting in the state owned properties such as 9170 km road network, 4748 km rail network, 89 severely damaged bridges and culverts, 411 schools and 138 national parks.

The paper presents a detailed analysis of the case study of 2013 floods in Lockyer Valley region in Australia to identify the critical failure mechanisms of road bridge structures exposed to flood events. In the region, 43 out 46 bridges were damaged due to the 2013 flood. Major failure mechanisms of bridge structures have been identified as scouring of abutments and piers, damage to bridge decks due to urban debris impact and severe damages to bridge approach ramps. A framework comprising of a combination of the concept of fault tree method and damage index is proposed for vulnerability modelling of bridges for an extreme event.