Queensland Premier Anna Bligh and Australian Prime Minister Julia Gillard have called the recent flooding in Queensland the “worst natural disaster in our history”. Three-quarters of the state of Queensland has been declared a disaster zone (source: Brisbane times). Flooding has affected over 200,000 people in the Fitzroy, Burnett, Condamine, Mary and Brisbane river basins (flood map here). A total of 41 deaths have so far been attributed to the flooding, and 67 people remain missing.
The worst flooding of the last 48 hours has affected the Brisbane river basin. Toowoomba. Grantham. Ipswitch. Brisbane. Each community in turn has borne the brunt of floodwaters from the Lockyer valley, with flood levels exceeding the great flood of 1974. Flash flooding in Toowoomba quickly inundated the town, catching many by surprise, and killing 10 people who were swept away by the fast-moving flood waters (video here). Over 40 people were plucked from rooftops by military helicopters, and search and rescue crews continue to search for missing people.
The Lockyer is a major tributary of the Brisbane river, which also continues to rise, and is forecasted to exceed the 1974 flood level of 5.5m some time tomorrow. With the lower Brisbane river continuing to rise, flooding is expected to peak tomorrow (Thursday, 13 January) in Brisbane. The latest flood models suggest that as many as 20,000 properties in Brisbane may be entirely flooded. Thousands of people have been evacuated, and many more face evacuation.
The level of the lower Brisbane river can be controlled to a degree, by modulating the release of the Wivenhoe dam, which is (at the time of writing) at around 190% capacity, and holding back more volume of water than Sydney harbour. The Wivenhoe dam was constructed following the disastrous floods of 1974, when 14 people lost their lives and 8500 homes were flooded in Brisbane and Ipswitch. This time, nervous flood modellers and dam engineers must try to strike a fine balance between spilling too much water from the dam (and exacerbating an already bad flooding situation in the lower Brisbane river valley), and holding back too much water, which could eventually cause the lake to overtop the dam. We will likely find out tomorrow or the next day if the right decisions were made.