The following information was taken from the BOM Climate Education
website
Some of the more intense low pressure systems outside the
tropics are capable of matching the power and destructive potential
of many tropical cyclones.
In a class by themselves in this regard are the class of
cyclones known as "east coast lows", which as their name implies,
develop near the east coast between southern Queensland and
Tasmania.
They are most common off New South Wales, where on average one
develops each year, in winter or the transition seasons. Such
systems can intensify very rapidly (pressure falls of 24 hPa within
24 hours are not uncommon). They are capable of generating violent
gales, at their worst approaching hurricane intensity.
One powerful system in June 1967 was noteworthy for the
extensive erosion of Gold Coast beaches. Drawing moisture from the
relatively warm waters of the Tasman Sea, these systems can also
produce intense, flooding rains; a noteworthy example was the
system that brought Sydney to a standstill in August 1986.
East coast lows have in fact been responsible for many of the
major flood episodes on east coast river systems - severe flooding
in eastern Victoria in June 1998 being a recent example. The
systems are a normal part of the climate of eastern Australia, and
have been hitting the east coast at least since European
settlement. One of the earliest descriptions of an east coast low,
in June 1820, can be found in the log book of Captain Phillip King,
who charted extensive portions of the Australian coastline between
1818 and 1822.
The Winter storms of June 1967
Occasionally the relative quiet of the Australian subtropics in
winter is disturbed by an east coast low, with its gales and flood
rains. One particularly severe storm in late June 1950 generated
hurricane force winds and 15-metre waves off the New South Wales
coast; and the heavily-flooded Clarence River carved out a new path
to the sea. In the remarkable month of June 1967, three such storms
battered the coastlines of southern Queensland and northern NSW,
generating major flooding and extensive erosion of Gold Coast
beaches. Six lives were lost.
"Synoptic chart for the storms of late June 1967. The tight
gradient indicates very strong winds; the long "fetch" of these
strong winds across the oceans off eastern Australia resulted in
huge swells that greatly damaged Gold Coast beaches."
The first system developed early in the second week of June,
bringing high winds and seas, and torrential rain. On the 11th, a
small low pressure centre developed off the Queensland coast,
triggering exceptionally heavy rain over Brisbane and surrounds. In
13 hours some 260mm of rain fell, and the 24 hour total of 282mm to
9am on the 12th was Brisbane's heaviest June rainfall ever.
Resultant flooding was said to be the worst since 1931. The heavy
rains extended several hundred kilometres north and south of
Brisbane, with vast areas under water, although flooding extended
inland only as far as the fringe of the Darling Downs. The
mountainous hinterland of the Gold Coast and northern NSW received
exceptional falls, up to 600mm within 24 hours.
There was to be no respite. The next depression developed off
southern Queensland on 21 June, bringing a renewal of strong to
gale force southeasterly winds and heavy rain over largely the same
areas as before. Rainfall was not so heavy, but falling as it did
on saturated soil, it was enough to cause further flooding. Gales
and heavy seas lashed the coast between southern Queensland and
central NSW. The Gold Coast beachfront, which had been pounded
relentlessly through June on top of a summer cyclone season that
had extended into April, was by now suffering serious erosion. A
third east coast low developed on 26 June, and became notorious for
the huge seas it produced. Gale force winds and huge southeasterly
swells, generated by an unusually long fetch across the southern
Coral Sea, sent mountainous waves crashing onto the crumbling Gold
Coast. Houses, buildings, and large sections of roads, undermined
by the waves, toppled into the sea. Damage would have been far
worse but for the efforts of hundreds of troops and thousands of
volunteers who spent days filling sandbags as a bulwark against the
huge seas.
Apart from the serious erosion of Gold Coast beaches, June 1967
was noteworthy for the extraordinary rainfall the storms dumped
over southeast Queensland and northeast NSW. More than 1,000mm fell
over the mountainous hinterland, with 1,631mm at Springbrook.
Brisbane's total of 647mm exceeded all but the wettest months in
the summer rainy season.
