Climate change is creating more extreme weather, and Australia is seeing a rising number of landslides, rockfalls and slope failures on its roads. Yet most governments and road owners still assess risks from road level and manually - leaving hazards unseen until they fail.

Geotechnical firm Civil Geotechnical Consultants (CGC), part of global engineering group RSK, says high-precision aerial assessment should become standard practice on high-risk corridors, so slope hazards are found and measured before they fall, not cleaned up afterwards.

Geoscience Australia identifies saturation of slope material from rainfall or seepage as a natural landslide trigger. Reports by the Bureau of Meteorology and CSIRO show that the intensity of short-duration extreme rainfall has increased by at least 10 per cent 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, and Australia now ranks second in the world for weather-related losses per capita. Yet most road authorities 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.

CGC director and geotechnical engineer Ian Thompson says: “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. 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.”

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.

CGC pioneered drone-based three-dimensional slope modelling in Australia and has been refining the technique since 2019. Ian says the technology 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. The same approach allows rapid assessments after a cyclone or storm, helping asset owners reopen roads safely within the tight windows that disaster-recovery funding allows.

“We can fly a site in an hour or two and build a three-dimensional model with high precision,” Ian said. “That kind of detailed rock-face mapping used to take three days with a geologist and a compass. Drone technology delivers much better information that governments and road owners can make safety decisions on.”

“At CGC, we’re seeing more extreme weather events, and we’re seeing them more often. Each year brings more disaster-related events, which means more slope failures, more risk and more assessments - and those events are reaching further south and further inland than they used to,” he added.

CGC is calling for high-precision aerial assessment to become standard practice on high-risk corridors - not to replace current methods, but to upgrade them - so risks are identified and accurately measured before they fail.

Ian says: “The highest-risk places are the ones you would expect: steep, uneven, high rainfall and not a lot of infrastructure investment.”

The same technology can be applied well beyond road slopes. CGC uses it to measure earthworks volumes and track construction progress, assess the risk of cuttings and embankments, and to monitor slopes for movement after heavy rain. Its assessments find risks for crews before they return on site. And after a rockfall, the technology can measure exactly how far debris travelled, so authorities can set evidence-based exclusion zones, fencing or signage. It can review hard-to-reach sites very close to buildings and is increasingly used for structural inspections such as bridges.

Visit: https://www.cgc.net.au