Road to resilience: navigating climate challenges in transport

Climate resilience is the ability to anticipate, resist, and recover from disruptive events while minimising their impacts.

Resilient infrastructure provides communities with the ability to bounce back quickly from disaster events, emerging stronger and more resilient to future events.

The ‘resilience lifecycle’ is a framework that involves preparing, preventing, protecting, responding, and recovering. For transport networks, this means proactive steps to safeguard infrastructure and ensure it can continue to function even in the face of extreme events impacted by climate-related hazards.

A comprehensive risk management approach is key to building resilience. This begins with mapping the effects of historical weather events to understand where vulnerabilities lie in the network.

Equally important is identifying potential future hazards and vulnerabilities like coastal erosion, landslides and flood-prone areas. But it’s not just about knowing where problems may happen - it’s also about recognising the importance of specific routes, and the consequence of failure of a particular asset.

Not every road is equal. We need to be strategic, investing more heavily in routes that are both critical and vulnerable to natural hazards. Asset owners need investment plans for their roading networks, so that an integrated approach to improving resilience is achieved. This starts at a strategic level but flows down to an operational level, so that people on the ground understand the expected levels of service and criticalities of each road corridor.

Planners and engineers should ask hard questions, such as whether it’s wise to renew an asset on a corridor that might be under water or beyond economic repair in short timeframes e.g., 25 years. Can we do things smarter and more efficiently in a funding constrained environment? Could we start to look at alternative routes now and get them designated so that when intervention becomes necessary, land has been set aside for this purpose? This would also help us know how much to invest in the maintenance and renewal of the existing asset.

An example of this is the Manawatu Gorge. This road had been subject to rockfalls and landslides for many years, and, finally, following a significant landslide, the road was closed while a permanent detour was planned, designed and constructed – all at high pace. If prior planning had identified this earlier, there could have been a less rushed business case, planning and land acquisition process. All of this could have been completed in advance of a significant event occurring, leading to the new highway being completed earlier and reducing continued investment in the old route prior to it being divested. For example, holding seals and minimal maintenance instead of renewals.

Preventative measures, such as inspecting and maintaining infrastructure, are also important. It’s about being prepared for the worst and ensuring roles and responsibilities are clearly defined, so we can swiftly act when disaster strikes. This might include having contracts in place with contractors and consultants for emergency works, as well as having early warning or alerting systems in place so that risk is identified and prepared for ahead of forecasted events.

Resilience starts with understanding current and future risk and ensuring this is incorporated into the solution. Infrastructure should be designed and constructed to optimise the balance between affordability and expected future resilience demand over the asset’s anticipated lifespan. For example, bridges and port assets that can be elevated in response to rising sea levels, as well as roads designed to be higher to avoid flooding.

Culverts, too, should be sized to accommodate heavier rainfall in the years to come, as well as their associated scour protection. There is often incremental cost in increasing the size of a culvert at the time of design and construction, compared to reinstatement and maintenance costs of an undersized culvert, not to mention any disruption during events.

Just replacing like-for-like because it’s the quick and easy approach is hard to justify when you consider the whole-of-life cost equation. Notwithstanding this, we need to consider the criticality of the asset and what an acceptable level of service is. For example, for an access road to be unserviceable for a few days per year is probably acceptable, so it might be acceptable to design to a lower level of service, providing the risk of significant damage to the asset is minimised (e.g. ensuring an undersized culvert isn’t going to scour the road away in an overtopping event).

We also need to look at better communicating the expected levels of service for our infrastructure. For example, to protect residential property, often urban roads are designed to be secondary flow paths during significant events. Meaning it’s actually expected that they are unserviceable for a duration of time post event, depending on their criticality.

In the aftermath of a disaster, restoring access to key transport routes is paramount. The priority should be making these routes safe and accessible, before undertaking more permanent repairs. Often, this requires a careful balance between speed of recovery and safety.

While reopening routes is often urgent, we must also weigh the safety risks and costs involved. Having a catalogue of pre-designed solutions, such as retaining walls, can help speed up the process.

For some routes, nature-based solutions like living retaining walls may be appropriate, offering a sustainable, cost-effective alternative to traditional engineering. For more critical infrastructure, however, hard engineering solutions may be necessary.

Data systems also play a crucial role in building resilience. After Cyclone Gabrielle, a highly effective geospatial system was used to record and prioritise recovery projects, helping ensure that the key lifelines were prioritised.

There are several easy wins that could significantly enhance the resilience of New Zealand's transport network. Simple measures, developing robust and automated trigger action response plans (TARPs), help ensure critical (and vulnerable) infrastructure has a proactive approach to risk management applied, and isn’t left to luck.

More flexible design standards, which would allow for the use of innovative materials that provide increased resilience and reduced carbon footprints are also important. Current standards can be quite prescriptive. There’s a real opportunity to rethink these standards to encourage innovation and flexibility.

Looking ahead, adopting a long-term vision is key. We need to begin with the end in mind. If we’re designing for the next 100 years, what do we expect our transport network look like? What routes do we want to continue to invest in and should we be divesting in some routes? Starting with this vision allows us to plan better, with resilience and whole-of-life performance at the core of our decisions.

Extreme weather events like heavy rain, floods, heatwaves, and rising sea levels threaten not only the safety and viability of our transport networks but the economic and social well-being of communities. Disruptions to transport can sever vital connections, disrupt supply chains, and drive-up repair costs. As seen in South Westland’s Epitaph Landslide, the Marlborough Sounds storm events and in the Coromandel, the impacts can be catastrophic.

With New Zealand currently spending up to $1 billion annually on emergency maintenance, targeted, preventative measures are not only essential, but a good investment. However, it’s often hard to quantify what the return on the investment is, due to the inability to easily measure how much the investment has saved in the long-term.

While we can’t predict the future with certainty, we can prepare for it. Forewarned is forearmed. By adopting a proactive, comprehensive approach to risk management, we can ensure that New Zealand’s transport network remains safe, functional, affordable and sustainable in the face of an uncertain future.

Let’s start by engaging with our key stakeholders around what levels of service we need and can afford for different corridors, and different scales of event. Let’s build an investment and recovery plan for our roading networks so when events occur (or are forecast), we have a plan and can action it immediately. We can’t afford to continue our current reactive approach to significant natural hazard events.