Inskip “sinkhole” will happen again on peninsula: report
EVENTS like the Inskip "sinkhole" happen somewhere along the Inskip peninsula about once a year but there is no way of predicting when or where they will happen, a government report says.
A Government report on the September incident says it was "definitely not a sinkhole" and did not appear to be linked to earthquakes that happened off the coast of Fraser Island in the months before the Inskip incident.
The report suggests several ways the State Government could limit risks to campers at Inskip Point, although it also says it was not clear whether those options were practical.
For the time being, Queensland Parks and Wildlife Service had established a buffer zone in high-risk areas. This had slightly reduced the available camping space, but National Parks Minister Dr Steven Miles said there was still plenty of space available.
"I recognise the importance of camping to the many families that make their annual pilgrimage to Inskip over the Christmas holidays and to the local Rainbow Beach economy," Dr Miles said.
"I can assure visitors and local businesses that there will be plenty of capacity at Inskip right across summer, and also plenty of space for campers at nearby Teewah Beach and Fraser Island.
"For safety reasons QPWS closed Inskip's M.V. Beagle camping area and the eastern section of the M.V. Sarawak camping area after September's near-shore landslip which caused a large, deep, submerged hole to form and swallow up a vehicle, van and camper trailer.
"We've kept 'lost' campsites to a minimum and reopened the two campgrounds, while keeping safety as the priority.
"QPWS now has a temporary barrier in place defining the buffer zone, and expects to have installed a permanent low fence, as well as safety, regulatory and interpretive signage, by Christmas.
"The signs will warn people of the dangers and explain the nature of the events, for which the triggers are unknown and future events cannot be reliably forecast."
In the longer term, options floated in the departmental report included:
- Avoid the risk by preventing camping on the beach and foreshore areas, restricting camping to susceptible areas, preventing or limiting beach driving, and considering moving camping to other areas.
- Reducing the probability of unexpected instability. This option needs more analysis over time as at this stage the triggers for these events cannot be determined.
- Reduce the consequences of instability by building deep rock walls or a high sand bund. Both options are likely to be expensive and impractical.
- Warning signs or systems. QPWS is considering further scientific monitoring of the sea floor, is putting up warning signs at the buffer zone, and will seek advice on how effective a warning system would be. A siren system would require training of campers, could be prone to false alarms through human error or misuse, and is not considered a practical option at this point.
The report says the incident was a "retrogressive breach flow slide".
"This is where a large body of sand moves quickly, forming a scarp (small cliff) that moves rapidly inshore as the sand debris moves out to sea," it says.
The reason for the incident were not clear, but most likely was related to " rapid, turbulent tidal flows acting on a steep off-shore slope of fine to medium-grained sand".