Swamped: the Tamar River's centuries-long battle with mud

Thomas Scott's 1832 plan of Launceston shows there was a narrow river channel in the Tamar Estuary with extensive mud flats and swampy land surrounding the area.

Fisherman's Creek emptied into the upper reaches, draining much of the town that was encroaching on the summer foraging land of the original inhabitants.

In 1847, the Cornwall Chronicle pleaded for the government to do something about dredging the mud from the Tamar.

Lieutenant-Governor William Denison visited Launceston the following year to see what could be done to facilitate shipping in the port.

He pointed out that as the tides ran rapidly, silt from various streams and rivers discharged into the Tamar, and mud banks collected and shifted irregularly, navigation would always be a matter of some difficulty.

Only part of Denison's plan was undertaken due to the cost.

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The first part was to build a jetty at the end of Charles Street, but it made matters worse by interrupting the natural flow of the river, and instead of clearing the mud, it collected it.

His further plans to remove the bar at the mouth of the North Esk, drain the swamp, and reclaim the riverbanks were repeated over the years in the belief that these "improvements" would allow the river to cleanse itself and stop ships from sitting in the mud at low tide.

Denison's ideas of constructing a lock, damming the North Esk, and building a swing bridge never did happen.

But as the population increased, the city grew and more land was cleared, larger quantities of earth emptied into the river.

A Priestman dredge removed mud from the riverbed and dumped in on Tamar Island and in the old shipping channel.

The arrival of the dredge Platypus in March 1898 caused much excitement, but two years later The Examiner complained that the "mud flats are not decreasing in area or offensiveness".

The mud, deposited further downstream, came back on the tide!

In 1940, an elaborate model of the Tamar River was constructed so the Marine Board could experiment with various ideas for mitigating flooding and preventing bank erosion.

These included determining the effects of installing groynes and training walls, a diversion canal between the North Esk and the Tamar, and a lock on the lower reaches of the Tamar.

WWII interrupted the experiments, but most ideas were deemed too expensive and were likely to increase both the flood hazard and silting in the upper reaches of the Tamar.

Since colonial times, the swamps have been drained, mud flats reclaimed, rice grass planted, and the river dredged and raked, but still, mud flats appear at low tide as they have done for time immemorial.