The Brisbane River is the major water source for Brisbane and it has a substantial catchment area. Its headwaters are in the Brisbane Range about 25 km north-east of Nanango and 140 kms from central Brisbane. The river and its numerous tributaries drain 13,500 sq km. The excellent, reliable water source that gracefully meanders towards the sea was the major reason for situating Brisbane in this location. However, the river also provides its dangers.
The year 1973 was one of the wettest known over much of Australia, and in keeping with the strong La Niña event that prevailed the 1973/74 northern wet season started early. By the end of 1973 large areas of the country were saturated. Then came January 1974, which featured probably the biggest continent-wide drenching since European settlement, inundating vast areas of the country.
In north Queensland, big floods on January 5th marooned cars and coaches across a broad area. The deluge then extended to northwest New South Wales on the 7th and 8th, causing flooding along the Namoi and Castlereagh rivers: railways and roads were cut, necessitating evacuations by helicopter.
On 11th January creeks in Brisbane burst their banks, flooding roads and streets. As monsoonal rains poured down, the Gulf Country of Queensland and extensive areas of the dry centre were turned into vast inland seas, isolating pastoral stations and causing heavy cattle losses. About 500 people were evacuated from Normanton and Karumba, while 250 stranded passengers on the Townsville-Mt Isa railway were air-lifted to Mt Isa. Some 400-600mm of rain inundated the southern Northern Territory and southwest Queensland in January, more than twice the average annual total at some locations.
On top of all this came tropical cyclone "Wanda", which moved ashore north of Brisbane on Thursday 24th January, producing relatively little wind damage, but sending down enormous quantities of rain over the Australia Day weekend. In Brisbane, intensifying rain throughout Friday dumped over 300mm within 24 hours. In three days the Queensland capital received 580mm, with even heavier falls over river catchments near the city (1,300mm in five days at Mt Glorious). The first houses were washed away along Enoggera Creek early on the 26th. As rivers continued to rise many more were lost. The Bremer River peaked at Ipswich on the Sunday and the Brisbane River peaked early on Tuesday; both at their highest levels since the disastrous floods of 1893. Fourteen people were drowned, some trapped in offices by the rising waters, 6700 houses were ruined and 5,000 people were made homeless.
(Information from the Bureau of Meteorology website.)
Boating on the Albion Park Racecourse
Swimming at the corner of Albert & Margaret Streets
Crossing Margaret Street
To claim this earthcache you must answer the following questions:
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Measure the maximum level of the flood in the Botanic Gardens on 29 January 1974. (Give it your best guess by comparing your own height.) From this estimate the extent of flooding in the city. Compare your answer to photographs or maps of the flooding that are available online. How close were your estimates?
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A second marker commemorates a different flood. Name the year and estimate the height of the flood waters. What difference would this have made to the extent of the flood?
Wander down to the river and observe its features. S27 28.350 E153 01.301 is in the middle of the river, but will give you an idea of the wider area you need to observe (i.e. both sides of the river and the nature of the river itself). Nearby you can catch a River Cat for an even better examination of the river.
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Describe the terrain at this point. What are the features of the Brisbane River that make it particularly prone to flooding? (Some you should be able to observe, but others you may have to research.)
Please do not put your answers in your logs, but email them to Doctor Owl for approval. Logs that have not been accompanied by the correct answers will be discretely queried and if necessary deleted.