Shipwreck Lake Illawarra emerges in full colour as CSIRO sonar shows its power

The wreck of the Lake Illawarra is brought into view in an image from CSIRO mapping of th

THE wreck of the Lake Illawarra, whose captain caused one of the worst disasters in Tasmania’s history when he lost control of the ship and it crashed into the central span of the Tasman Bridge in 1975, springs from the sonar scan like a colour-coded ghost.

The ethereal image was produced using a $300,000 multi-beam echo sounder operated by CSIRO scientists, who have for the first time mapped the ship in its watery grave. The Illawarra lies 34m below the surface of the Derwent River, just south of the bridge it destroyed on the night of January 5, killing 12 people.

The CSIRO modelling shows what lies ahead for research in Australia’s oceans, water systems and, potentially, in the search for Malaysia Airlines Flight MH370.

“The historical significance of this is of great interest to me and, I’m sure, to the people of Tasmania,’’ hydrographer Matt Boyd said. “You can see the wreck in its entirety and make out the detail of the spans from the bridge itself.’

Little has been seen of the ship since the disaster, aside from murky diver photos, but its hold on a community literally torn in two by the disaster has been constant. While the loss of life was catastrophic — a 126m span of the bridge fell on to the bulk carrier and killed seven crew members, and four cars carrying five people fell from the bridge — the ­social fallout was a slower, more complex phenomenon.

East and west Hobart were in essence separated for years. Crime rates fell in the west, where police were based, but jumped in the east. The eastern suburbs, after dealing with the shock and economic fallout, began to function independently, with more schools, social functions and jobs.

Maritime Museum of Tasmania curator Rona Hollings­worth said the accident still held the public’s attention. “Perhaps it shows just how reliant we are on infrastructure, perhaps because it had such huge social consequences on Hobart society,” she said.

“The CSIRO has showed us stunning still and video images of the wreck site. The museum will be showing the images on a loop in the Lake Illawarra display.”

The sonar is a baby version of what will appear on the CSIRO-operated, $120 million RV Investigator, which arrived in Hobart earlier this month. The ship is capable of mapping the ocean floor to any depth using the same system but with a trade-off in resolution.

“You can take this system into places you’d never be able to get a ship of that size and find cool stuff, but equally you can take a big ship like that into the ocean and find stuff you’d never get with a small boat,” hydrographer Stuart Edwards said. “This is in fairly shallow waters: 35m at 400 kilohertz. When we map full ocean depth on Investigator down to maybe 10,000m, we’ll be operating at 12khz. Detail wouldn’t be there.”

The CSIRO would not comment on whether the Joint Australian Co-ordination Centre had held talks with the agency about co-opting the Investigator for the search for the missing airliner. It is understood that even if this did happen, it would take the ship 3.8 years, non-stop, to map the 60,000sq km search area.

Aviation mysteries aside, CSIRO team leader Tara Martin is focused on collecting data that may help put the jigsaw of our oceans together. Dr Martin said oceanographic models were useless without depth measurements and that these provided “boundaries” for “practically every branch of marine science”.

“We are using the system to look at what type of sea floor we have, whether it is sandy, muddy, coral reef … that’s used by our ecologists to understand what habitats there are on the sea floor and therefore what types of creatures might be living there.” This could set a standard to be referenced for “hundreds of years” and inform climate change, and ­resources and fisheries management.

The oceans are the final frontier. Australia has mapped just 12 per cent of the ocean floor in its economic control. The data will be made available to anyone who asks, particularly scientists who want to use the measurements to inform their research.

About 200 years ago, Mr Edwards said, one of the first hydrographic surveys spanned the Atlantic Ocean. “It took them three years, they collected something like 800 soundings,” he said.

“We can collect 400 soundings with every ping of this system and it can ping up to 50 times a second. Feel free to do the math.”

 

Article Source: THE AUSTRALIAN

Image Source: CSIRO