A road pavement on a bridge that has been significantly damaged by rain and flooding.

How to make roads more resilient instead of a bottomless pit of money

Widespread damage to eastern Australia’s road network during the flood crisis has highlighted the need to rethink road management, a researcher has said.

Rain, storms and flooding have damaged large sections of the road network, causing thousands of potholes and billions of dollars in repair bills.

Recent flooding and rains have caused an estimated $2.5 billion in damage in New South Wales alone, while in Victoria the state government says it has so far completed 89 000 potholes in less than six weeks.

The damage has also made travel less safe, with NSW Regional Roads Minister Sam Farraway urging caution even after floodwaters recede.

“While our crews are working around the clock to repair potholes and damaged roads, they simply cannot keep up with the current volume of work,” Mr Farraway said.

“Please don’t assume that just because a road is open, it will look like the road you are used to.

“Slow down and drive towards new conditions as you find them.”

Temora Shire Council in southern New South Wales estimates its damage bill could be as high as $6 million.

Mayor Rick Firman said it was frustrating to see the damage.

“We can’t control the weather, thank God, but…you never thought you’d be praying for the rain to stop,” Cr Firman said.

Susceptible to damage

Michael Moffatt, technical manager of the Australian Road Research Board, said the materials widely used to create roads were more susceptible to the impacts of extreme weather events, but were also the best solution available.

He said most of the country’s roads are made of different types of crushed rock, covered with pulverized joints such as bitumen.

A man stands in front of pavement fragments in an office meeting room.
Michael Moffat says crushed stone pavements are more susceptible to water damage.(Provided: Michael Moffat)

Dr Moffatt said the material becomes vulnerable when it rains.

“Water is a softening agent. It penetrates the rock, it seeps into the voids between the rock, it softens the material,” he said.

“It then acts as a lubricant between the rocks and stops the hard engineering bond you get between the pieces of stone.”

Dr Moffatt said the low cost of bitumen was one of the reasons so many Australian roads were covered with it.

“The mere fact that we have a wash road there is partly because we can use materials that are more sensitive to moisture than others would use overseas,” he said.

“It’s fair to say that our crushed stone pavements with a sprayed joint are more vulnerable to water damage than an asphalt or concrete sidewalk.

“But then again, they’re much, much cheaper to build, so we have a lot more of them.”

A composite of two roads with potholes and road damage caused by rain and flooding.
Damaged roads can be seen across eastern Australia, including the Temora region.(Provided by: Temora Shire Council)

Solutions to change the dial

Other materials, such as concrete, can be used to pave roads.

But Dr Moffat said the cost of using them instead of crushed rock would add an “astronomical” price tag to weatherproofing Australia’s roads.

“You could certainly reduce the risk significantly if you had unlimited budget, materials and capabilities to build [these roads],” he said.

With climate change making extreme weather events more common, Dr Moffat said the best way to build resilience in the road network was to rethink the way they were managed and maintained.

A roadway that has been significantly damaged by rain and flooding.
The town of Wagga Wagga in southern New South Wales is one of many areas struggling with damaged roads.(Provided: Wagga Wagga Town Council)

“I think relying entirely on ‘we’ve always done it this way’ is open to some questions, because ‘this way’ may no longer reflect current conditions,” he said.

“I think we need to at least ask ourselves if the maintenance levels we have are adequate for a world where we expect more water, more often.

“We need to keep our water off our sidewalks better than we do now if we’re going to have a system that doesn’t take the damage it’s taking now.”

Dr Moffat said monitoring and maintaining roads more frequently and using technologies such as in-situ stabilization could help reduce the risk of potholes and damage.

eyes in the sky

A research project looked at using drones to photograph the road network and feed the images into a digital model that could help predict when potholes might occur and when maintenance was needed.

The technology could be used by road managers, such as councils or state governments, to supplement the work done by people on the ground.

Three men stand in a parking lot, photographed by a drone in the air.
Cristobal Sierra and his team test their drone technology.(Provided: Cristobal Sierra)

Cristobal Sierra, a researcher at Swinburne University, said road maintenance revolves around planning for repairs or reacting to problems.

He said the use of drones would help make it more obvious when roads needed fixing.

“So we have the ability to fix problems before they actually happen, which would reduce the overall cost,” Dr Sierra said.

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