Enhancing resilience by considering climate change influenced bushfire in slope risk analysis

Bushfires cause immediate disruption to road corridor access and commonly lead to short-term road closure due to debris; however, erosion and landslides can occur after subsequent significant rainfall, which cause far greater long-term disruption to the service levels of the road. Debris needs to be removed and, in some instances, significant slope stability work is required to make the road safe, resulting in prolonged downtime and road network disruption. As a result, communities, emergency services, and key industries including freight and tourism reliant on the network, may experience significant impact. Climate change is expected to worsen the situation; with the frequency and severity of bushfires expected to increase, due to warming temperature, rising drought factor, increased intensity of rainfall, and a greater occurrence of thunderstorms. Infrastructure Victoria’s Adapting Victoria's Infrastructure to Climate Change study showed a 50% increase in the annual probability for loss of life and a 100% increase in direct and indirect costs from bushfire and increased rainfall slope risk under a 2070 future climate for an exemplar rural road in a bushfire prone area (Arup, 2023). While constraints in capital investment for significant upgrades in critical road infrastructure limits the capacity for roads to be immune to bushfires, there is a significant opportunity to reduce the disruption caused by associated bushfire hazards. This reduction then enhances the resilience of the surrounding network and communities. This paper presents an expansion and enhancement to traditional slope risk management practice for roads across Australia to address the impact of bushfires and subsequent landslides on road infrastructure assets in a climate-resilience context. It builds on the nationally applied Transport for New South Wales (TfNSW) Slope Risk Analysis (SRA) framework and integrates climate change and community resilience into the methodology, by assessing variable temporal risk states (current, current with bushfire, post-bushfire, and future climate) and consideration of community risk through consequences based on resilience criteria. The enhancement to traditional practice allows for a more comprehensive understanding of landslide risk considering bushfire with climate-change. The expanded assessed risk levels allow for assessment of proposed mitigation and adaptation measures to support more informed decision making in concert with industry resilience and sustainability strategies where climate is considered in every decision made.