The bright lights beaming off the Tamar River at night are caused by a ship tasked with clearing sediment from the estuary.
On Monday night the ship’s bright lights could be seen by residents in Trevallyn and higher parts of Launceston.
It is tasked with scouring the river to remove silt and provide a clearer water flow.
The Upper Tamar Estuary has been affected by a silt build-up for more than 200 years.
It has been recognised a build-up of sediment has an adverse impact on the effectiveness of the Tamar flood levee protection scheme, designed to prevent flooding of the low-lying areas of Launceston.
In 2013 about 200,000 cubic metres of sediment were removed during that year’s raking program.
Launceston Flood Authority general manager Andrew Fullard confirmed the ship was in operation.
"We are targeting areas near North Bank, the Seaport and other areas of the Upper Tamar Estuary,” he said.
"We will only continue operating while the river flows remain high, but silt raking is an ongoing task that will need to be carried out into the future to keep the river clear of sediment."
Mr Fullard said there was no schedule for the ship’s operation.
"We have contracts in place with the operator of the raking vessel to ensure we can be reactive and flexible when higher flows are occurring; there has been some recent rainfall in the upper catchments which have produced these higher flows and they present an opportunity to clear sediment,” he said.
Proposed silt-problem solutions
Change the river flow
In 2016 a longtime Tamar estuary researcher believed the silt problem could be solved by redirecting Tailrace flows through a canal on the river’s western side.
Ian Kidd, who was completing a PhD on estuarine science, has estimated that this waterway could remove 285,000 cubic metres of silt from the Yacht Basin.
Mr Kidd said the plan would address flow issues with the Tamar and would be an alternative to releasing the South Esk River.
Controlled water release
In 2015 the Tasmanian Government, Launceston Flood Authority and Hydro Tasmania began a trial to assess the effectiveness of a controlled release of water from the Trevallyn Dam coordinated with silt raking operations on the removal of silt from the Tamar estuary.
Dredging won’t work
In 2012, research from Monash University showed the 200 year-old siltation problem in the Tamar River is a symptom of broader environmental damage and will not be solved by dredging alone.