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On 12 June 2023, heavy rain caused water to flow over the sides of a flyover at the northbound Junction 1 on the M1 in Brent Cross, resulting in a “waterfall” from the flyover onto the cars below. A video taken at the scene made for dramatic footage – and for National Highways director of environmental sustainability Stephen Elderkin, was a stark illustration of a much broader problem.

“There is no doubt that climate change is with us,” Elderkin says. “However well we do on mitigation, we need to plan for a wetter, hotter, windier future.”

In parallel with aiming for net zero emissions across its operations, road maintenance and construction, and road user emissions by 2050 through the Net Zero Highways plan, National Highways’ approach to climate resilience for the Strategic Road Network (SRN) encompasses flood protection, condition monitoring, business continuity, temperature resilience and risk assessment.

National Highways has submitted  three reports to the Climate Change Committee under the Adaptation Reporting Power (ARP) process required by the Climate Change Act 2008. The reports were submitted in 2011, 2016 and 2022, with a fourth submitted in 2023 on a voluntary basis. Elderkin notes that the reporting process along with other related initiatives has clarified that risks to infrastructure from climate change emerge from three sources: heat, wind and water.

Elderkin does acknowledge that rising summer temperatures pose an increasing threat – “We’ve seen 40°C days that translate into much higher temperatures at the surface of the road. We’re up to 50°C-plus in terms of the temperatures recently measured in the asphalt around our network.”

Dry, compacted ground can exacerbate flooding, while other future heat-related threats include the risk of wildfires, he notes. Strong winds are another concern, with infrastructure owners increasingly looking at ways to defend assets from them.

“However, I’m most worried about the wetter future,” says Elderkin. “That’s because water, if it’s not well managed, has multiple challenges. If it pools on the surface, that’s a safety risk. You can end up with subsidence of banks with all the consequences that come with that from higher rainfall.”

Infographic created by Buro Happold for NCE

Flood risk a priority

This sense of urgency around flood risk aligns with the National Flood Risk Assessment in England, last updated on 22 January. The update stated: “Around a third (38%) of all roads are in areas at risk from one or more sources of flooding. If we apply the climate change projections the percentage of the road network in areas at risk rises to 46% by the mid-century. This is an increase of 21%.”

Unsurprisingly, drainage has been a focus for National Highways. “We updated our standards to increase the capacity of our drainage in 2006 and we’re currently in the process of updating them again,” says Elderkin. “In 2006, we increased the required capacity by 20%. We’ve then taken the latest scenarios from government and created catchment-level increases in capacity that will be required for building drainage in those areas, and they range between 20% and 35%.”

However, upgrading drainage capacity is only a partial solution. “The challenge is that much of the road network was built in the 1960s and ‘70s, so most of our drainage pre-dates those recent capacity increases,” he says.

“So, what do we do about the 93% of the drains that were built without allowance for climate change? Digging up 93% of our drainage to put in larger drains would be prohibitively expensive and the customer impact would be enormous. The carbon impact would be enormous too; the strategy has to be hybrid.”

Nature-based solutions

That hybrid approach does encompass hard engineering and new materials, but Elderkin says nature-based solutions (NbS) represent a longer term pre-emptive way to address climate change.

He cites the Moors for the Future Partnership, National Highways’ “biggest and most ambitious yet” intervention in terms of nature based flood management.

Set to commence this winter, the scheme is a collaboration between several organisations including National Highways and the Environment Agency and aims to restore the degraded peatlands of the Peak District and South Pennines.

“By helping regenerate the moor – re-wetting the moor, putting in dams to hold back water – you reduce the risk of flooding, and you also reduce the risk of wildfires,” says Elderkin. “That’s good for us and it’s also great for carbon reduction, because of the carbon sink effect of peat – instead of the peat being eroded, it’s building up. It’s also good for biodiversity.”

The scheme will build on previous projects including a scheme at Fillongley village near the M6 in Warwickshire, which has been flooded six times since 2007. Through National Highways’ Reconnecting Fillongley project, Warwickshire Wildlife Trust worked with farmers and landowners on a network of 15 wildlife-rich wetlands and pools, and 3km of riverside enhancements.

Elderkin emphasises however, that the continued success of such schemes will rely on “a more joined-up national approach to nature-based flood management” going forward.

Catchment-level thinking

That view is echoed by the Jacobs and AtkinsRéalis joint venture appointed as National Highways’ environmental and sustainability technical partner in June. The three-year contract will see the AtkinsRéalis-Jacobs JV work with National Highways to support the delivery of its Environmental Sustainability Strategy.

While a key aim of the JV is to achieve net zero emissions across England’s 7,200km of motorways and major A-roads by 2050, assuring the climate resilience of the SRN is also a priority.

Jacobs director of operations Iain Blackwell confirms an initial aim of the JV is to assess resilience across the network on a national scale, noting that a critical shift is being made by National Highways towards a more proactive, preventative approach that includes NbS.

AtkinsRéalis net zero director – transportation Simon Shapcott says the JV recognises the importance of catchment-level, systems thinking.

Specifically, it will need to account for the importance of embedding systems thinking throughout National Highways, and across the full asset life cycle.

“It’s often at an organisational level where this can become challenging because it’s a business transformation or a behavioural change piece including operations and management. For example, if a designer is looking at a plan and there’s no reference to climate change, it would be great if they were thinking, ‘Is this going to be effective from a climate impact perspective in 30 or 50 years’ time?’ You need everyone across the organisation and the sector to be thinking about this.”

Aecom head of strategic consulting – surface transportation Joanne Edwards agrees. She notes: “I don’t think there’s a single magic bullet when it comes to materials or innovation in terms of future-proofing and climate resilience.”

A system-wide approach to climate resilience can be divided into operational, tactical and strategic strands, she says. “The operational strand is things like asset management plans, the tactical entails choice of materials and their durability, and the strategic strand looks at the proactive future-proofing standards and behaviour change. All the strands are equally significant.”

She agrees that embedding this thinking so that it becomes business as usual is critical. “I think a radical shift is needed in terms of bringing industry up to speed. The whole civils and infrastructure community has got to buy in to new solutions so we can do the research and get them into the standards.

“From innovative materials to biodiversity net gain, there are lots of levers that you can pull, but it’s being aware of them and using them in the right place that’s going to provide the fix.”

Aecom technical director – operations & maintenance Matt Pearson adds that prior to pulling those levers, a true picture of climate resilience needs on the network is required.

“In my experience, we can get confused between a problem caused by climate change and a problem caused because an asset is at the end of its life, or hasn’t been maintained.

“Often, we’ve just not done the drainage maintenance, so we don’t understand if that drainage is at capacity or not.”

“First, you want to understand your network, inspect your network, understand your assets, understand what condition they’re in and understand if the basic maintenance has been undertaken or not. Once you get to that point, you can start to measure the volume of rain that would lead to a flood. You can assess whether your drainage is working as it was designed to work.”

Arriving at a baseline of the road network’s climate resilience needs remains a challenge, he says.

Through National Highways’ Reconnecting Fillongley project, Warwickshire Wildlife Trust worked with farmers and landowners on a network of 15 wildlife-rich wetlands and pools, and 3km of riverside enhancements

Forecasting and planning

Beyond that baseline, scenario planning is key. Buro Happold’s future scoping for climate resilience interventions on roads includes established solutions such as raised embankments to mitigate flood impact and smart monitoring of sustainable drainage systems supported by real time data.

It also encompasses energy resilience through localised renewable energy microgrids and reinforced structures for wind resilience. In addition, it is looking at the use of stabilised base layers and more moisture-resistant low carbon and base materials, as well as innovative materials such as self-healing asphalt.

Buro Happold strategic pursuits director for UK public sector infrastructure Samuel Wrightman concurs that currently, flooding and surface water management are key priorities.

“Flooding is becoming more frequent and severe. The need to manage those flood zones and surface water therefore requires new solutions, whether that’s enhanced drainage, soakaways, permeable materials, or even ground stabilisation of banks.”

Buro Happold partner and UK bridges lead Edmund Metters notes that reacting to current challenges must also be extrapolated into utilising data to forecast climate impacts.

“It’s about forecasting the climate change and the weather patterns that are going to affect the roads and the associated structures. That relies on a huge amount of data and the more data that we can analyse and provide insights from, the more we can think ahead.

“Our use of GIS and multi-criteria assessment provides a picture with potential ways of predicting how things will be moving in the future,” says Metters.

“At a National Highways-level, you’re looking at a suite of assets across a large area, including the knowledge about them, the changing weather patterns and the impact from a climate resilience perspective. Then you can start playing with those levers and potential scenarios.”

Buro Happold transport and mobility associate Ed Downer adds: “From a planning perspective, I think when we’re starting to look at where things might go in the future, that’s where that systems-based approach can be beneficial.”

He notes that rising temperatures could be a bigger part of the picture over the longer term. “Taking a look at past trends and extrapolating those to come up with one vision of the future, we need to think about the variability of what possible futures might emerge from where we are now. That includes thinking about just how dry or how wet the UK could get.”

Wider behavioural factors, such as how much people will travel on roads, are also considerations, Downer says.

“So, for long distance travel, is there anything we can do to encourage increased use of the rail network, be it for freight, be it for personalised long distance transport? All of this has the potential to help us to sweat the asset longer term and put a fewer stresses on it.”

Given the evolving climate picture, clients and government “really need to look at how to drive the longer term outcomes that we’re all looking for,” Wrightman concludes.

“It goes back to taking a much longer term outcome-focused approach. This has to be about the country gearing itself more towards long-term missions rather than short-term outputs.”

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