The sight of a house sliding down a hillside on the Mornington Peninsula had many calling for action. But what can engineers do?
A weatherboard house lies splintered at the base of a steep hillside, looking more like a failed children’s art project than a $2 million trophy home.
Last week’s landslide at McCrae on the Mornington Peninsula destroyed one house, injured a council worker and saw around 20 neighbouring properties evacuated pending urgent assessment.
The dramatic escalation to a series of landslides on the peninsula – there have been at least another two recent events in the area – has put homeowners on edge.
The cause of this landslide is currently unknown: geotechnical and groundwater assessments are ongoing, the Mornington Peninsula Shire said.
But the event raises broader questions about the safety of buildings that often predate planning controls for landslides, the effect climate change might play in increasing the occurrence of such events, and the role of engineers in mitigating the risk of further landslides.
Upward trend
“As a general principle, the more we can preserve the natural landscape, the less chance of causing landslides,” Darren Paul, Lead Technical Director Geotechnical and Tunnels at WSP Australia, said. “If we alter natural systems by impacting natural surface and subsurface flow paths, or undertake earthworks, we risk causing or exacerbating landslides.”
A rainstorm the weekend before the Tuesday landslide and subsurface water flow are considered likely to have played a part in the McCrae hillside collapse. More frequent, intense rainfall events is an example of the influence climate change is likely to have on the frequency of future landslides around Australia.
“Due to increased rainfall, we had a whole spate of landslides in the 1980s and 90s, and then we went into a drought,” Paul said. “Landslides were less frequent until about 2011, when we had an exceptionally wet summer. Now, we’ve just had three La Niña years in a row and there has been a significant increase in landslide frequency over that time.”
Significant events have included the collapse of a cliff near Bells Beach that killed a man in 2021 and another fatal event that killed two people in the Blue Mountains in 2022.
“What it shows us is that the propensity of landslides is linked to changing climate conditions. If it gets drier but with more intense rainfall events, we could see an increase in certain types of landslides.”
Mitigating the problem
Can a landslide be prevented? While mitigation measures to prevent landslides occurring are available, they can require significant engineering works which might not be practical to implement.
Mitigation measures addressing both the likelihood of landslides occurring and the associated consequences can be complex and may require significant engineering works.
“It can be a bit like earthquakes,” Paul said. “We can’t prevent them, but we can reduce their impact by avoiding development in areas prone to landslides or designing structures to resist their effects.
Miner, meanwhile, suggested it is “more about recognising landslide susceptibility in the landscape, and designing sustainable and appropriate development“.
For Paul, retrospective landslide mitigation is complex.
“Landslides, in some cases, are just natural processes – and it’s a case of there should never have been a house put there, as the landslide risk is just too high,“ he said. “There are other situations where human influence has worsened or created a landslide hazard – poor earthworks or allowing uncontrolled water infiltration into the ground we shouldn’t have, for example.
“In those situations, there’s probably more that can be done. Because we’ve created the issue, we manage it.”
Practical measures focus on two areas. Controlling groundwater with drains, wells and pumps tackles one of the major causes of landslides. The other side of the coin is stabilising a slope, which uses measures such as piles, retaining walls and steel bars grouted into a hillside, known as “soil nails”.
Other mitigation methods include retaining existing vegetation as much as possible, which can help prevent soil wetting, and reinforcing slopes by planting trees. Building channels or deflection walls can also help direct water away from landslide-prone ground.
Geotechnical engineer Tony Miner said landslide causes can be split into preparatory factors and triggering factors.
“Sometimes it’s the actual land itself; its geological material and steepness,” he explained. “Then we have these triggering events, generally an intense or prolonged rainfall that increases groundwater. Mitigation has to potentially tackle those two things.”

A matter of timing
The best way to manage landslide risk lies in appropriate planning. Planning overlays taking landslide hazards into account, which require geotechnical assessment for any proposed build within their boundaries, have been widespread since the early 2000s.
But as the events at McCrae show, these controls don’t deal with widespread legacy issues of buildings predating planning controls.
“Homeowners are usually content to live with the hazard until a situation like this invokes community concern. We study how we can retrospectively approach it,” Paul said.
Mitigating works can be hugely expensive, and doing so in an established residential area is more difficult thanks to practical constraints associated with property boundaries, property access and council regulations.
Homeowners retrospectively subject to a landslide planning overlay are under no legal obligation to have an assessment performed on their property. Engineering experts agree, however, that it would be a good idea.
Resources for engineers
The 1997 Thredbo landslide that killed 18 people was partly the impetus for the Australian Geomechanics Society (AGS), part of Engineers Australia, to develop a set of guidelines relating to landslide hazards. Initially released in 2000, the AGS Landslide Risk Management Guidelines were updated in 2007 and are currently undergoing another revision, due to be released in 2026.
Widely viewed both nationally and internationally as state-of-the-art industry documents, the guidelines are extensively referenced in planning schemes. As Co-Chairs of the revision steering committee, Paul and Miner say the updates will consider technological advancements from the past 15 years while also prioritising flexibility and transparency in methodology, and increased accessibility of the document to end users.
“It was recognised that we could make things more readable,” Miner explained. “We are emphasising the need for better communication between technical people, such as engineers and non-technical people, such as council regulators and homeowners.”
The AGS also conducts a landslide assesment training course which highlights risk assessment techniques and provides access to a number of landslide types in the field. The next four-day course will be held in November.
Miner points out that making assessments of landslides is difficult, with an inevitable degree of uncertainty: “There’s a perception that science is infallible but we’re trying to emphasise the significant uncertainties around geohazards. We don’t have all the answers about what’s under the ground.”
For Paul, it takes an event like McCrae to get attention and funding for the problem: “I think there will continue to be more landslides as the climate changes, and we have to do more about it.”
Durban in South Africa had a similar problem 50 years ago on the “Bluff”, effectively a sand dune. The cause was unregulated discharge of roof and surface rainfall run-off down the slopes which caused slope undermining and instability. Control through infiltration pits reduced the problem.