Yarra Ranges Shire bid to extend planning controls as new maps identify growing landslide threat

Hi-tech maps have pinpointed which properties in the Dandenong Ranges are at risk from “likely” landslides and falling debris.

More than 13,000 properties in the Dandenong Ranges are at increased risk of being wiped out by landslides, prompting a push from the local council to extend planning controls.

New 3D maps commissioned by Yarra Ranges Shire Council identified 13,400 properties were exposed to potential damage or destruction from landslides or falling debris.

The suburbs and towns found to be the most vulnerable included Belgrave, Monbulk, Montrose, Mount Dandenong and Warburton.

The maps replaced hand drawn versions previously used by the shire and were commissioned after the Dandenong Ranges was smashed by a severe storm in 2021.

At least 71 houses were left uninhabitable and a further 51 damaged by wild winds that also brought down tens of thousands of trees.

Yarra Ranges Shire commissioned the new maps after the Dandenong Ranges was smashed by server storms in 2021, destroying homes like this one in Olinda. Picture: David Geraghty

Councillors this week voted unanimously to expedite interim planning controls for building in vulnerable areas after the expert report warned that the region’s next significant rainfall event or landslide was looming.

“There are no certainties about when the next significant rainfall event or landslide could occur,” the report stated.

“However, given recent weather patterns and high instance of emergencies in Yarra Ranges it is reasonable to consider this likely and imminent.”

Before and after images of the January 14 McCrae landslide. Picture: Supplied

Mayor Jim Child said while the changes may cause some concern it was important the council worked to keep the community safe.

“We’re already used to living with bushfire as a risk and for some of residents they need to be aware that there is a risk of landslide too and this is something we can manage and live with,” Mr Child did.

“Over the past few years there have been several landslides in our municipality and following the incident in McCrae (Mornington Peninsula) this has been headline news with a Board of Inquiry currently taking place.

The January 14 McCrae landslide destroyed a house, injured a council worker and forced the evacuation of up to 19 properties.

The residential area does not have an erosion management overlay, a potential oversight revealed by an independent Board of Inquiry probing the landslide’s cause.

The Yarra Ranges mapping identified 3172 new properties were now at risk from landslides but 1185 covered by the old modelling were no longer vulnerable.

The 3D technology also identified 498 properties in the path of potentially deadly debris flows, where material including toppled trees could flow rapidly down a slope causing “a significant risk to life”.

Debris flow channels were identified in residential areas south of Warburton, near The Basin and on Mount Dandenong.

Yarra Ranges wants its erosion management overlay to cover thousands more properties, seen here in purple. Picture: supplied

The council was warned it could face legal action and “significant reputational damage” if it did not act on the report’s findings”.

“Given the new EMO mapping has already been prepared, but not yet introduced

into the planning scheme, there is a risk to council if a landslide occurs within one

of these areas, similar to the landslide at McCrae,” a council report stated.

Properties included within an EMO are not automatically prohibited from development, but the planning approval process can be more complex and costly.

Geotechnical and landslip risk assessments would most likely be required and the proposed works would need to be engineered to reduce risk levels to a tolerable limit, a council report says.

If the landslip risk was too high or the property was also in a debris flow susceptibility area a permit may be refused because of the risk to human life and property.

State Planning Minister Sonya Kilkenny has to approve the interim controls, however, they could be rolled out more quickly than permanent erosion management overlays which could take at least 12 months to introduce.