The northeast of Tasmania is often noted for its relatively benign climate, and certainly receives much less rain than the western half of the island State. It is, however, prone to very heavy rainfall over periods of a few hours to a few days. These events, associated with intense depressions moving down the east coast of the mainland, or developing in situ, can produce intense rainfall over periods up to 72 hours, triggering major flooding. The worst such event in recorded history was in April 1929, when 22 people died.
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Heavy rain began in northern Tasmania on the night of Wednesday 3 April, reached a peak on Thursday, and did not clear until Saturday. Accompanied by northeast winds, the highest falls were in the high country of the north-east, with a secondary area of heavy rain south of the Burnie/
Ulverstone area. In both areas, up to 500 mm fell in three days. At
Mathinna in the northeast, 337mm fell in the 24 hours to 9am on the 5th.
On the Thursday afternoon, the Briseis
Dam, built only a few years before on the Cascade River, gave way above
Derby. The resultant torrent rushed down the narrow
gorge of the Cascade River for three
miles to the township, carrying with it thousands of tons of trees, boulders, rocks and gravel. Houses and offices were overwhelmed,
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At Avoca, the river rose some 17 metres above summer level and by the time the waters receded, the railway station had vanished. Railway tracks were undermined and twisted, bridges were washed away, and landslips blocked the line. Many road bridges throughout the north and northeast were lost.
On the north coast, most rivers were heavily flooded. At
Gawler, near
Ulverstone, a truck crashed through a
bridge into a flooded river, drowning eight people, including six from one family.
Flood waters converged from east and west on the Tamar Valley, causing the river to rise to record levels. An enormous mass of water poured through
Cataract Gorge on Friday night, and combining with floodwaters from the North Esk, inundated more than 1000 houses in the low-lying parts of
Launceston. Some 3500 people were evacuated. The major power station at Duck Reach was washed away.
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Scenes of devastation - landslides, gullies scoured of vegetation (and even soil), as
well as the destruction of man-made structures - were widespread throughout northern Tasmania. It took many weeks to repair the damage.
In southern Tasmania the rain was not so heavy, but was sufficient to cause rivers to overflow across roads, and to inflict heavy stock losses. Southeasterly gales accompanying the rain swept the Derwent Valley on the Thursday night, taking roofs off houses and branches off trees.
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