Widespread damage wrought on eastern Australia's road network during the flooding crisis has highlighted a need for a rethink about how roads are managed, a researcher says.
Rain, storms and flood inundation have damaged large sections of the road network, causing thousands of potholes and billions of dollars in repair bills.
Recent flooding and rain has caused about $2.5 billion in damage in New South Wales alone, while in Victoria, the state government says it has so far filled 89,000 potholes in less than six weeks.
The damage has also made travel less safe, with NSW Regional Road Minister Sam Farraway urging caution even after floodwater had receded.
"While our crews are working around the clock to repair potholes and damaged roads, they simply cannot keep up with the volume of work at present," Mr Farraway said.
"Please don't assume that just because a road is open it is going to be anything like the road you are used to.
"Slow down and drive to the new conditions as you find them."
Temora Shire Council, in southern NSW, estimates its damage bill could be up to $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 rain to cease,' Cr Firman said.
Susceptible to damage
Australian Road Research Board state technical leader Michael Moffatt said 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 were made from different types of crushed rock, surfaced with sprayed seals such as bitumen.
Dr Moffatt said the material became vulnerable when it rained.
"Water is a softening agent. It gets into 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 bits of stone."
Dr Moffatt said the low cost of bitumen was one of the reasons why so many Australia roads were covered in it.
"The mere fact that we have a road there to get washed out is partly as a result of us being able to use the more moisture-sensitive materials than others would use overseas," he said.
"It's fair to say that our crushed rock pavements with a sprayed seal are more vulnerable to water damage than an asphalt or a concrete pavement would be.
"But then again, they are far, far cheaper to construct, and so therefore we have a lot more of them."
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 weather-proofing Australia's roads.
"You could certainly reduce the risk enormously if you had unlimited budget and materials and capabilities to construct [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.
"I think relying entirely on 'we've always done it this way' is open to some question, because 'this way' may no longer reflect current conditions," he said.
"I think we at least need to ask ourselves the question as to whether or not the maintenance levels we've got are suitable for a world where we're expecting more water, more often.
"We need to be keeping our water out of our pavements better than we are now if we wish to have a network that doesn't suffer the damage that it does now."
Dr Moffat said monitoring and maintaining roads more frequently, and using technologies such as in-situ stabilisation, could help reduce the risk of potholes and damage.
Eyes in the sky
A research project has examined using drones to photograph the road network and feed the images into a digital model that could help predict when potholes could happen and when maintenance was necessary.
The technology could be used by road managers, such as councils or state governments, to supplement the work done by people on the ground.
Swinburne University researcher Cristobal Sierra said road maintenance revolved around either scheduling repairs or reacting to issues.
He said using drones would help make it more obvious when roads needed repair.
"So we have the ability to fix issues before they truly arise, which would reduce the cost overall," Dr Sierra said.
