Civil engineer says high-risk road corridors should be routinely 3D slope-mapped to identify hazards locations before landslides fall.
According to Civil Geotechnical Consultants (CGC), landslides and rockfalls are rising on Australia’s roads as extreme weather intensifies, but the way that danger is currently assessed isn’t keeping up.
CGC director and geotechnical engineer, Ian Thompson, says most governments and road owners still assess slope danger much as they have for more than 15 years — an engineer standing at road level, sketching and photographing a slope where the upper parts are not visible to them.
This raises the risk of hazards remaining unseen until they fail and fall.
“When you assess a slope from the road, you often can’t physically see the top of it, so you’re making educated guesses about what’s up there,” said Thompson.
“If you don’t find a hazard, you never understand the risk. If you find it but get it wrong, you’re either underestimating the risk or spending public money on a risk that may not exist.”
A worsening weather situation for landslides
Geoscience Australia identifies saturation of slope material from rainfall or seepage as a natural landslide trigger.
Reports from the Bureau of Meteorology and CSIRO show that the intensity of short-duration extreme rainfall has increased by at least 10% in some parts of Australia in recent decades, with the largest increases in the north.
And the costs are growing: insurers incurred $2.19 billion in claims from declared extreme-weather events in 2023–24, with Australia now ranking second in the world for weather-related losses per capita.
As a result, as extreme weather worsens, Australia could see more slope failures near roads that no one saw coming, with more road closures, more communities cut off and more risk to motorists alongside those slopes.
Making safer decisions
According to Thompson, drone-based 3D slope modelling now enables engineers to fly a high-risk site in under two hours, identify hazards invisible from the ground, build a model accurate to the centimetre and create a baseline to track changes in risk profile over time.
“Drone technology delivers much better information that governments and road owners can make safety decisions on,” he said.
“The highest-risk places are the ones you would expect: steep, uneven, high rainfall and not a lot of infrastructure investment.”
The same approach enables rapid assessments after a cyclone or storm, helping asset owners reopen roads safely within the tight windows that disaster-recovery funding allows.
Related reading on landslide risk:
Modelling rainfall-induced landslide risk
NZ’s online landslides map will be vastly expanded
