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Tamar silt a recurring problem for Launceston

Siltation in the upper reaches of the Tamar River had become so bad in 1886 that the Marine Board of Launceston sought urgent funds for dredging from the Tasmanian government.

At the marine board meeting on July 27, it was stated that the Tamar River was "the highway of the colony" and the sooner the dredging was carried out the better.

A report by civil engineer Napier Bell estimated that 300,000 cubic metres of silt needed to be removed to keep the boat channel open between the mouth of the North Esk River and Tamar Island.

The cost was put at £50,000 (about $5 million in today's values) but the board's request received a favourable reception.

Silt build-up would be a continuing challenge for the Marine Board of Launceston that was established by Act of Parliament in 1857.

The marine board acquired its first dredge in 1878. But the steam-driven spoon dredge, that used a canvas bucket dragged under a barge, proved unsatisfactory in removing silt near the North Esk wharves.

It was modified with a metal grab, manufactured by the English company Priestman, and removed silt from the river until 1885 when it was replaced by a steam bucket-dredge Platypus.

Port of Launceston historian Sir Raymond Ferrall notes that the Platypus dredger was heavy, uneconomical, and lacked mobility but effectively dealt with silt for many years.

Mud and gravel dredged by the Platypus was repurposed to build-up riverbanks and reclaim land along the North Esk and the Tamar.

The Examiner of September 10, 1904, reported that a silt pumping plant was being used to reclaim 20 hectares of land near Town Point.

"In consideration of raising Crown land and making it of greater value the Government has agreed to give the necessary money for installing the plant, and assist in other work of the same kind."

The pump was installed on a pontoon that enabled it to be readily moved to any depositing area.

"The necessity for this addition to the board's plant arose through the filling up of all the depositing areas, and if the former system of dumping from the hopper barges had to be continued the silt would have had to be towed to Rosevears."

The spoil, which was 60 per cent water, was being discharging ashore at the rate of 1025 tons per day by the silt pump.

The Examiner reported that 600,000 tons of silt would be required to complete the reclamation work and at the present rate of discharge it would take two years.

When plans for new wharves in Home Reach were drawn up more dredging was needed.

A new dredge, the Ponrabbel, was ordered from Scotland on the eve of World War I, but it was sunk in 1914 by the German warship Emden on its way to Launceston, a casualty of the global conflict.

Its replacement arrived in the Tamar in 1921 and became a familiar sight for another 50 years.

TOP IMAGE: The Marine Board of Launceston’s silt pump on Home Reach depositing soil on the Western Swamp, Inveresk in 1904. Picture: Tasmanian Mail, September 24, 1904.

MIDDLE IMAGE: The silt pump pipeline filling up flat land on the Western Swamp, Inveresk with silt from the Tamar River in 1904. Picture: Tasmanian Mail, September 24, 1904.

BOTTOM IMAGE: Marine Board of Launceston’s dredge Ponrabbel before being sunk by the German warship Emden in 1914. Picture: Weekly Courier, July 30, 1914.

(Written for the Launceston Historical Society and published in the Sunday Examiner on 29 August 2021)


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