Utilising laser scanner and unmanned aerial vehicle (UAV) geotechnical data capture to manage visitor safety in the Buchan Caves

Some of the most impressive limestone cave formations in Victoria are found in the Buchan Caves Reserve. The caves are part of the Buchan–Murrindal cave system, located on Gunaikurnai Land and hosted in a large outcrop of Devonian-age cave and karst-forming limestones. The Reserve is one of East Gippsland’s major tourism attractions, visited by large numbers of local, interstate and overseas tourists annually. Although the caves at Buchan are old (sediments sampled from within the Buchan Caves have been dated at greater than 750,000 years), ongoing periodic rockfalls into the caves, part of a natural process known as ‘breakdown’, are anticipated. The likelihood of breakdown events within engineering timescales poses potential risks to the visitor caves. A Maptek SR3 underground laser scanner and above-ground UAV photogrammetry have been used in combination to capture a 3D spatial relationship between the cave system and ground surface terrain. The resultant digital model assists in visualising this relationship, allowing for accurate identification and mapping of locations where breakdown hazards may be more likely to occur. The model also provides baseline data for future scanning that can help identify and monitor ongoing ground deformation. A geotechnical risk framework has been developed to assist Parks Victoria understand and manage the relative risks posed by cave breakdown, providing a formalised approach to managing safety in the Buchan Caves.