The Tamar is at risk

By Jim Collier

The Tamar tourist and recreation Basin is nothing more than a muddy bowl. Small vessels currently moored there are already sitting in mud at low tide; even 15 years ago these boats were swinging free at all stages of tide.

Experts are now conceding that even a one in 50-year flood event would lead to significant property damage and an emergency evacuation response in the low-lying suburbs of Launceston.

The Tamar — as a magnificent feature of Launceston — is at risk. The loss to tourism and stay-over holidaying is also in jeopardy.

AS THE years and decades roll on, it is now abundantly clear that the decision-makers and government politicians have turned their back on the Tamar River and its people of Launceston.

It was so convenient for the State Government two elections ago in 1998 to talk up their plans and policies to ‘tackle the Tamar River silt problem’. Despite some futile efforts to dredge the silt from the main channel of the upper Tamar, over much of the draining catchments, it has been business as usual.

Like the Murray Darling, deprived of its natural flow, it is suffocating under massive amounts of sediment and it simply cannot survive under such a sustained onslaught.

These images are incredibly graphic; they show long term neglect and public denial. The once grand Tamar Estuary — just over 200 years since its discovery — has two very serious environmental problems.

A lack of natural water flow through the lower Esk Rivers and Cataract Gorge (except at extreme flood surges), and
A rapidly increasing siltation of the upper Tamar Basin

Both problems are interconnected.

The effect was dramatic

A diverted water flow down the Cataract Gorge now passes through the Trevallyn Power Station. Natural flows down the Gorge of 20-50 cubic metres per second — before the Trevallyn Dam was built — are now capped at 1.5 cubic metres per second. The effect is that natural scouring and flushing doesn’t occur with disastrous consequences for the Tamar Basin, in terms of silt deposits and water quality.

It’s only at flood times when waters overtop the Trevallyn Dam when flows of over 1,000 cubic metres per second can occur.

In late 2003 the Hydro power station at Trevallyn was shut down for maintenance over 2 months; this allowed increased flow through the Gorge. The effect was dramatic.

Under the current 1.5 cubic metres per second controlled flow, siltation in the Basin is increasing. To illustrate the gravity of this, I can recall 25 years ago I dropped an outboard motor in the river off the Tamar Yacht Club pontoon. In order to recover it I had to wait for low tide when a friend in diving gear retrieved it. Today, at exactly the same location, I would simply wait for the mud flat to emerge and lift the motor off the river bed!

The Tamar tourist and recreation Basin is nothing more than a muddy bowl. Small vessels currently moored there are already sitting in mud at low tide; even 15 years ago these boats were swinging free at all stages of tide.

Futile attempt

Launceston City Engineers concede that mechanically removing the 30,000 cubic metres of silt deposited each year is a recurrent and futile attempt at ‘doing something’. The very serious social impact of this situation is the effect the silt build up will have in the event of a major flood. The increased amount of mud in the Basin effectively limits the space for the rising river waters. As I pointed out in an earlier Tasmanian Times article, The saga of Tamar silt, this calls into question the effectiveness of the city’s flood levy system.

Experts are now conceding that even a one in 50-year flood event would lead to significant property damage and an emergency evacuation response in the low-lying suburbs of Launceston.

The Tamar — as a magnificent feature of Launceston — is at risk. The loss to tourism and stay-over holidaying is also in jeopardy.

I say again: Who could love this River? — We could!

Earlier: The saga of Tamar silt