In the past few years, the number of severe weather events in our region has increased, resulting in significant damage to infrastructure from landslides and/or flooding.
The floods that widely impacted the east coast of NSW in recent years will live long in our memories. Lismore, located on a flood plain, was particularly badly impacted in 2022, with several deaths, massive damage to property and long-lasting psychological pain. When mega-cyclone Gabrielle hit New Zealand in early 2023, the repair bill from the massive amount of flooding and landslide damage was estimated at $9–14.5 billion. Vanuatu’s government declared a state of emergency after it experienced an unprecedented two cyclones in rapid succession.
These extreme events are frightening and damaging during their peak. Communities also shoulder profound and long-lasting impacts in the aftermath. Without functional infrastructure, affected communities can lose connection with essential services such as schools or hospitals, and businesses can struggle to get their wheels turning again.
Maintaining or rapidly restoring functionality after adverse events such as these depends on re-establishing links to essential services. With resilient infrastructure, recovery after extreme events can be quicker and less costly, both in human and economic terms.
Resilient design requires early intervention and planning
WSP’s Technical Director Graham Scholey has expertise in managing geotechnical risks to major infrastructure projects. He has been working with a number of clients along the east coast of Australia to assist them to manage design repairs to road infrastructure damaged by floods and landslides.
He says that for transportation networks, the optimal level of resilience depends on a range of factors including economics and cultural needs.
“Achieving resilient design in road projects requires early intervention by the owner at the planning stage,” he says. “The focus should be on limiting the susceptibility of the infrastructure to hazards, as well as on implementing design measures that allow functionality to be restored quickly after a severe event.”
In New Zealand, adoption of design resilience has progressed over the last 25 years, largely driven by the need to respond to earthquake events. WSP has been central to planning and implementing resilient design approaches to road projects in New Zealand, including the Transmission Gully project and the road network in Wellington.
Pathmanathan Brabhaharan, National Technical Leader – Geotechnical Engineering and Resilience, WSP NZ, gives an example of adopting resilient design early in the planning process for a highway, where a high level of resilience was required for the route given the limited alternatives. The adopted approach was to construct the highway on embankments that could be rapidly restored using conventional earthworks equipment, instead of viaducts which could take months to rebuild.
Restoring damaged infrastructure is an opportunity to embed resilience
Graham says that while every repair or restoration project is an opportunity to embed greater resilience, there are usually a range of complex factors to navigate, such as differing stakeholder priorities, limited budgets, tight timeframes or restrictive delivery mechanisms.
“While disruptions from floods and landslides to major highways generally have the greatest adverse impact on the community, smaller and less frequently used roads can sometimes become a bigger headache for asset owners when it comes to balancing costs and benefits,” he says.
“As an example, an asset owner was forced to close a road with very low traffic volume because of significantly increased landslide hazard activity following prolonged heavy rainfall in 2022. WSP used quantitative geotechnical risk assessment techniques to demonstrate that the cost for landslide stabilisation and road repair would be many times more than the value of the asset, running into tens of millions of dollars. The owner of this asset had constrained capital works budgets and was reliant on government disaster recovery funds.
“WSP’s assessment helped the asset owner secure funding for the reconstruction of the road on a new alignment. While this is a positive outcome for the community and asset owner, it still draws on public funds to restore the original function. WSP is working with our client to select and design the new road alignment, which will unavoidably still be exposed to inherent natural geohazard risks. The most sustainable way of managing these residual risks is to adopt a resilient design philosophy with a strong focus on maintaining serviceability.”
Balancing financial resources and functionality
While ‘building back better’ is ideal, Graham points out that, “in reality, constrained budgets or schedules often restrict the design options for restoration of damaged infrastructure. Ultimately, compromises may be needed to achieve the highest level of resilience possible within the budget envelope, required timeframe or available equipment and resources.”
For example, in a recent project in NSW, the surface of a local road was largely destroyed when flooding damaged an embankment carrying the road across a floodplain. The road was closed for weeks to allow for repair.
“The flood waters had risen to about 7m above the road level,” says Graham, “which meant that the only sure solution to keep the road open during future flood events would be an elevated bridge over the floodplain.
“Given limited funding and the prohibitively high cost, this solution was highly unlikely. An alternative would have been reconstructing the road as a floodway, accepting that the road would be closed during major flood events but would be able to be reopened rapidly and with limited clean-up as flood waters recede. In this example, limited project funding only allowed for some resilient measures to be adopted.”
Graham emphasises that smart, resilient designs are a balance of financial resources and functionality.
“A robust design may be one that enables partial rapid restoration of infrastructure functionality where financial resources are limited,” he says.
Not all roads are created equal – but they all require resilient design
Getting smarter about the design of essential infrastructure means thinking more carefully about the adverse long-term impacts of poor decision-making and the economic and human costs of post-event reconstruction.
“It’s encouraging to see this perspective being applied by governments in Australia,” says Graham.
“The New South Wales Government’s Future Transport Strategy acknowledges the importance of a resilient infrastructure system. It embeds a requirement for new infrastructure projects to address long-term resilience risks and for existing projects to ‘build back better’. These strategic objectives need to be incorporated into contracts that include resilience as part of design compliance.”
“Only by thinking smarter can we collectively respond to the challenges we face from climate change. In Australia, New Zealand and the Pacific, this means responding to the immediate impacts with future-focused thinking and building resilience to prepare for increasing shocks and stresses on our national infrastructure.”
With a Future Ready™ lens on resilient infrastructure, WSP is eager to work with our clients to help communities stay safe, remain connected, and thrive both now and long into the future – whatever that future holds. For more information on how we can work with you, please contact Graham Scholey, or go to our Geotechnical and Tunnelling services page.
About the Author:
Graham Scholey, Technical Director WSP, is a geotechnical engineer who has been helping clients solve ground engineering problems for over 35 years. His particular interest is in the management of geotechnical risks to major infrastructure projects. Following several recent severe weather events along the east coast of Australia Graham has worked with our clients to assist them to manage the risks of landslide and design repairs to damaged road infrastructure. He is also Vice President (Australasia) for the International Society for Soil Mechanics and Geotechnical Engineering.