Charts of the Past
with Blair Trewin
BAMOS
Jun 2020
35
23 September 1916
The 1916−18 La Niña event, sandwiched between two major
eastern Australian droughts in 1914−15 and 1918−19, was one
of the most significant on record. It began in mid‐1916 and
continued through 1917, with the Southern Oscillation Index
reaching record high values at a range of timescales during
1917.
Whilst the La Niña was less extreme in 1916 than it became the
following year, winter 1916 was still very wet through many
parts of eastern Australia. It was the second‐wettest winter
on record for the Murray‐Darling Basin, with records being
set in parts of northern Victoria, inland New South Wales and
South Australia. Southern Victoria escaped the wet winter, with
near‐average rainfall, and remained relatively dry and warm
through the first three weeks of September.
The rain event began as a front approached South Australia on
the 21st. This moved across western Victoria on the 22nd, before
a near‐stationary trough developed on the 23rd, stretching from
north to south across much of the continent. Lows developed
on this trough in western Queensland and western New South
Wales, moving southeast to be over southeastern New South
Wales by the 25th and placing Victoria in southeasterly flow.
The low then became very slow‐moving, remaining over, or just
offshore from, eastern New South Wales for more than a week
(with a large blocking high in the Bight) before finally moving
out to sea after the 4th.
The heaviest rain over most of Victoria was on the 22nd and
23rd. 25 to 50 mm fell on the 22nd in much of southwestern
Victoria and a band stretching northwest into outback South
Australia, but the heaviest falls in central Victoria were on the
23rd, with numerous sites north of Melbourne exceeding 100
mm, including 113.8 mm at Kyneton. Melbourne itself had 108.7
mm over the 23rd and 24th, and went on to receive 174 mm
in six days, the start of an extremely wet period which meant
that, after being slightly below average as of mid‐September,
the city’s rainfall ended up being the highest on record for the
full year.
The heaviest rain shifted into northeast Victoria on the 24th and
25th, with 127.0 mm at Strathbogie on the 24th and 99.6 mm
at Moyhu on the 25th. As southeasterlies became established,
heavy rain then fell on the 26th and 27th in areas exposed to
the southeast, especially the Strzelecki Ranges in Gippsland
(where Balook had 318.7 mm in two days), the Otways and
northwest of Melbourne. Significant rain continued in the most
exposed areas until the 30th. By then it had also become a
major rain event for coastal New South Wales, with Milton going
on to receive 696 mm in the week ending 6 October. Some of
the most exceptional rainfall accumulations for the event were
northwest of Melbourne; Burncranna, near Mount Macedon,
had 483 mm from 22−30 September with six days over 50 mm,
while Blackwood had 385 mm. The rain in this period alone was
enough to exceed any other monthly totals ever observed in
the region.
Most Victorian rivers had flooding of some kind. The most
extreme flooding was in north‐central regions, where
catchments were already saturated from winter rains, and
many of the dams which regulate the rivers today did not yet
exist. The Goulburn River at Seymour and Shepparton, and the
Broken River at Benalla reached record levels, while Echuca had
its highest flood of the 20th century. The Yarra and Maribyrnong
also had significant flooding. Mooroopna was almost entirely
inundated after a levee failed, whilst Echuca, Shepparton,
Benalla, Seymour and parts of Melbourne all had many
properties inundated. At least 15 deaths were attributed to the
floods. There was also flooding in coastal New South Wales.
Wet conditions were widespread for much of the following
year, including the disastrous Clermont flood of December. It
also became exceptionally cool; spring 1916 was Australia’s
third‐coolest on record (including November snow on the
Mount Lofty Ranges), whilst summer 1916−17 and autumn
1917 were both the coolest on record.
Synoptic chart for 0900 AEST, 23 September 1916.