Tasmania is situated on a stable continental plate far from the nearest active plate boundaries, so it is a reasonable assumption that the range of geohazards to be expected is somewhat limited. However those hazards that do exist in Tasmania pose real risks to people, structures, infrastructure and the environment. To address these geohazards a modern risk assessment methodology is increasingly being applied throughout Tasmania.
A standard risk assessment approach to any phenomenon that may impose harm on our society is to measure consequences against likelihood. This allows us to make judgements on the acceptability of particular hazards, to compare various hazards against each other and to aid communication of the risk. Furthermore, it can be a powerful tool in order to develop strategies for lowering risk by exploring various management options.
The principal geohazards considered by Mineral Resources Tasmania (MRT) fall into two groups – mass wasting and tectonic hazards. Climatic hazards such as floods and storm surge, and environmental hazards such as acid sulphate soils, dispersive soils/tunnel erosion and bush fire are considered by other State Government agencies.
The mass wasting hazards considered by Mineral Resources Tasmania are landslides (i.e. slides, rock falls and debris or earth flows) and karst subsidence. Other forms of soil-related hazards, such as soil creep, soil erosion and swelling/shrinking associated with reactive soils, which may be important locally, are generally considered by other State agencies.
The tectonic hazards considered by MRT are earthquakes and tsunamis.
Currently the majority of the work conducted on geohazards by MRT is focussed on landslide hazards, particularly on the production of the Tasmanian Landslide Map Series and developing the MRT Landslide Database.
For many of the geohazards the possible consequences and likelihoods are poorly understood and justify further research. Indicative probabilities suggest that these hazards are much lower than others such as bushfire, although until specific risk assessments are undertaken a low likelihood does not necessarily imply a low risk if the potential consequences are considerable.
A conservative risk management approach undertaken by scientific organisations such as MRT and Geoscience Australia is to produce susceptibility and hazard maps. These maps make it possible to develop planning tools and emergency management strategies that, if used appropriately, can make a real difference to community safety.