The above ghostly image of the MV Lake Illawarra at the bottom of the Derwent River in Hobart was made with sonar.
Australia’s peak science body, the CSIRO, recently took delivery of a EM2040c, a High Resolution Multibeam Echosounder or shallow water sonar which can map the sea floor to 500 metres.
Matt Boyd and Stuart Edwards from the Geophysical Survey and Mapping Team at CSIRO and Andrew Pender from the Institute for Marine and Antarctic Studies went out in the IMAS vessel Morana to calibrate the new machine.
MV Lake Illawarra, a 135 metre long bulk carrier, is lying in 34 metres of water on the southern side of the Tasman Bridge.
Mapping the shipwreck took about an hour.
The EM2040c is mobile, can be lifted by a single person and can fit on almost any vessel. The system generates a fan shaped acoustic beam called a swath, and this swath can be up to four times the water depth in width. It’s able to send and receive signals at a rate of 50 times per second.
On January 5, 1975, the 135 metre bulk ore carrier MV Lake Illawarra was heading up the Derwent River in Hobart to offload 10,000 tonnes of zinc ore concentrate.
The ship drifted towards the eastern shore of the Derwent, striking two of the bridge pylons. Three spans of the bridge and a 127 metre section of roadway came crashing down into the river and onto the vessel’s deck.
Twelve died. Five were in cars on the bridge. They went over the gap, falling 45 metres into water. The others were trapped crew members of the MV Lake Illawarra.
There’s more on the shipwreck in the video clip:
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