An inquiry has called for “largely forgotten” landslide risks to receive greater attention after investigating a slip that destroyed a house in Victoria.

The state board of inquiry found the landslide that wrecked a hillside home at McCrae on the Mornington Peninsula on January 14 was caused by water that leaked from a burst water main. 

The main, owned by South East Water, had leaked for several months before being repaired last New Year’s Eve. Residents had reported concerns to the water company and Mornington Peninsula Shire Council. 

No one knew what the source of pooling water was or appreciated the seriousness of landslide risk, the inquiry found.

The delay in repairing the leak and redirecting water from the site may have contributed to the landslide. 

The inquiry report says it can be difficult to determine the cause of a landslides because both natural and human factors may be involved.

Regulatory barriers to mitigation include limitations in state planning policy and how councils and landowners can manage risk on private land.

The report says insurer CHU hired structural engineering company Logocon to determine the cause of the slope failure and assess “claimed building distress” to a strata property on Point Nepean Road, McCrae. 

Logocon found slope failure was caused by a reduction in the shear strength of sand soils, leading to instability. It pointed to unusually high rainfall the day before the slip, increased soil moisture due to the water main leak, and removal of vegetation.

It said had the slope been “constructed at a safe and compliant angle, failure would not have occurred under the imposed conditions”.

Logocon’s preliminary slope stability analysis indicated the proximate cause of the slip was inadequate construction of the slope at an excessively steep angle.

Read the board of inquiry report here.