Sinkhole hazards in Tasmania

Subsidence and collapse have occurred in surficial mantles of glacial, glaciofluvial, periglacial and alluvial origin that are widespread overlying karstified rocks in Tasmania. Sinkholes have formed in several areas within a few years of forests being cleared for pasture or by the timber industry. These sinkholes have probably resulted from increased water movement through the regolith due to decreased transpiration, coupled with the rotting of tree roots that formerly helped bind the regolith. Other sinkholes have formed at some road margins, particularly where culvert design is poor, and some of these collapses have damaged roads. Sinkholes that are probably the result of groundwater pumping have formed adjacent to a large limestone quarry. Because economic losses associated with individual sinkhole incidents have generally been comparatively minor, and because the incidents have been geographically dispersed, they have attracted little official attention. However, the individuals affected may suffer significant personal loss and the combined cost of karst-related land surface instability in Tasmania is probably signif icant.