The Hunter Valley Floods (also known as the Maitland Flood) of 23 February 1955 was a major flood on the Hunter River in New South Wales, Australia. They were one of the most devastating natural disasters in Australia's history.
The flood overwhelmed rivers on both sides of the Great Dividing Range, creating an inland sea the size of England and Wales. Worst hit was the inland city of Maitland, which is sited precariously on low-lying land on the Hunter, and which on this occasion was completely inundated by floodwaters. A total of 25 lives were claimed during a week of flooding that washed away 58 homes and damaged 103 beyond repair. In Maitland alone, 2,180 homes were invaded by water.
Heavy rain owing to the influence of La Niña had been occurring over the catchment of the Hunter River since October 1954[1] when, on 23 February 1955, an extremely intense monsoonal depression developed over southern Queensland and north-east New South Wales and moved southwards.[1][2] The very strong and extremely moist northeasterly airflow meant that over the basin of the Hunter and parts of the Darling River, rainfall amounts for a 24‑hour period were the highest since instrumental records began around 1885. Around Coonabarabran, as much as 327 millimetres (over 13 inches) fell in a single day, whilst falls in the upper part of the Hunter Basin the following day were generally around 200 millimetres (7.9 inches).[2]
With such heavy rain on already very wet ground the Hunter, along with tributaries of the Darling (Castlereagh, Namoi and Macquarie especially). reached levels quite unprecedented since measurements were first taken about 100 years earlier. For instance, the Namoi's discharge, normally only about 25 cubic metres per second (880 cu ft/s), reached a massive 9,000 cubic metres per second (320,000 cu ft/s), whilst the Macquarie peaked at around 6,100 cubic metres per second (220,000 cu ft/s).
In Maitland the Hunter exceeded its August 1952 record height by nearly a metre,[1] flooding as many as 5,000 homes with as much as five metres of muddy water.[3] 15,000 people were evacuated,[1] most by boat or helicopter, whilst 31 homes were never rebuilt. In Dubbo, four thousand residents were evacuated as the main street was under more than a metre of turgid, muddy water,[1] and the same thing occurred all along the Macquarie River, and at Gilgandra, a third of the buildings were completely destroyed.[1] A hole torn in the main street was later found to contain two large semi-trailers.[1]
The floods took altogether the lives of 25 people.[1] Some 2,000 cattle and many thousands of head of other livestock were drowned.[1] The damage to bridges, roads, railways and telephone lines took months to repair. There also were millions of pounds worth of crops destroyed.
Below in a timeline of the six days over which Maitland was ravaged by floodwaters:
At the time of the Hunter Valley flood, there was no system in place to monitor and predict the height of rivers, the likelihood of flooding, nor was there an effective system for disseminating this information.[7] Some of these functions were done by State governments, but they were not nationally coordinated.[7] The 1955 flood provided the political impetus for the federal Bureau of Meteorology to develop a national flood monitoring and forecasting service.[7]