7 August 2019

Deviot, Tasmania: the impact of a slow moving landslide on home owners

Posted by Dave Petley

Deviot, Tasmania: the impact of a slow moving landslide on home owners

In Australia today, news agencies are reporting a dispute between the government and home-owners over the impact of a reactivated, slow-moving landslide.  The location is Deviot in Tasmania, where a landslide is slowly destroying five properties.  It is a common, and extremely sad story of the impact that a landslide has had on everyday lives.

The location is -41.226, 146.924 – there is good Google Earth imagery of the site, taken in early 2016:-

Deviot landslide

The site of the landslide at Deviot in Tasmania. Imagre via google Earth, collected in January 2016.

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In 2013, during a period of heavy winter rainfall, the landslide at this site in Deviot reactivated, causing structural damage to a house.  Further significant damage occurred in 2016, with the movement affecting five houses.  At least one has had to be demolished.  Such an event is usually a disaster for the property owners, as in most jurisdictions domestic insurance does not cover landslide damage.  The level of impact of the landslide is dramatic:-

Deviot landslide

Structural damage caused by the Deviot landslide in 2016. Image by Nick Daking (the property owner) via ABC News.

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This story, which is far from unique, has come to prominence because the property owners allege that the local authority were fully aware of the landslides at this site, but failed to inform the property owners of the hazard.  The situation is being considered in the Upper House of the Tasmania Government.

Interestingly, there is a detailed geotechnical report on the site online (NB PDF), written this year by a geotechnical consultant, Dr Derek Pennington.  This includes a map, from 2011, which shows the extent of the relict (historic) landslide and the portion that has reactivated, causing the property damage:-

Deviot landslide

The 2011 MRT geomorphological map showing the Deviot landslide. Extracted from the report by Dr Derek Pennington.

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The report also demonstrates that the landslide reactivated during unusually wet periods:

Deviot landslide

The rainfall record showing periods in which the Deviot landslide reactivated. Figure extracted from the report by Dr Derek Pennington.

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This situation is a tragedy for the householders, who will have suffered huge financial loss and enormous stress.  It is simply the case that an ordinary property owner cannot possibly anticipate this sort of hazard.  Whilst I cannot really comment on the rights or wrongs of the case going before the parliament, we have to recognise that the system is not working correctly when potential property owners have no way to know that their site is at risk, and that there is no mechanism to insure against the risk.  This needs to be addressed as it is occurs again and again around the world.