page_title: 2010–11 Queensland floods
section_title: Background
hierarchical_section_title: 2010–11 Queensland floods / Background
caption_attribution_description: English: Track map of Tropical Cyclone Tasha of the 2010-11 Australian region cyclone season. The points show the location of the storm at 6-hour intervals. The colour represents the storm's maximum sustained wind speeds as classified in the Saffir–Simpson scale (see below), and the shape of the data points represent the nature of the storm, according to the legend below. Saffir–Simpson scale Tropical depression≤38 mph≤62 km/h Category 3111–129 mph178–208 km/h Tropical storm39–73 mph63–118 km/h Category 4130–156 mph209–251 km/h Category 174–95 mph119–153 km/h Category 5≥157 mph≥252 km/h Category 296–110 mph154–177 km/h Unknown Storm type Tropical cyclone Subtropical cyclone Extratropical cyclone / Remnant low / Tropical disturbance / Monsoon depression
context_page_description: A series of floods hit Queensland, Australia, beginning in November 2010. The floods forced the evacuation of thousands of people from towns and cities. At least 90 towns and over 200,000 people were affected. Damage initially was estimated at around A$1 billion before it was raised to $2.38 billion. The estimated reduction in Australia's GDP is about A$30 billion. As at March 2012, there were 33 deaths attributed to the 2010–11 Queensland floods with a further three people still missing.
  Three-quarters of the council areas within the state of Queensland were declared disaster zones. Communities along the Fitzroy and Burnett Rivers were particularly hard hit, while the Condamine, Ballone, and Mary Rivers recorded substantial flooding. An unexpected flash flood caused by a thunderstorm raced through Toowoomba's central business district. Rainfall from the same storm devastated communities in the Lockyer Valley. A few days later, thousands of houses in Ipswich and Brisbane were inundated as the Brisbane River rose and Wivenhoe Dam used a considerable proportion of its flood mitigation capacity. Volunteers were quick to offer assistance, and sympathy was expressed from afar.
context_section_description: Brisbane experienced major flooding in 1893 and 1974 as the Brisbane River broke its bank and inundated low-lying areas. Towns, including St. George and Theodore, had dealt with major flooding earlier in 1996.
  The floods were a result of heavy rainfall caused by Tropical Cyclone Tasha that combined with a trough during the peak of a La Niña Modoki event. The 2010 La Niña Modoki weather pattern, which brings wetter conditions to eastern Australia, was the strongest since 1973. This La Niña event caused a prolonged event of heavy rainfall over Queensland river catchments. Record or near record sea surface temperatures were recorded off the Queensland coast in late 2010. December 2010 was Queensland's wettest on record, with record-high rainfall totals set in 107 locations for the month. The state's average rainfall level of 209.45 millimetres (8.25 in) exceeded the previous record of 200.1 millimetres (7.88 in) set in 1975. 2010 was also recorded as the state's wettest spring since 1900, and the Australian continent's third-wettest year. Climate scientist Kevin Trenberth thought climate change was a contributing factor in the unusually high precipitation rates. He attributed a half-degree Celsius rise in ocean temperatures around Australia to global warming (which produces extra water vapour and intensifies the monsoon).  Other scientists say that it is too early to draw such a conclusion. Assertions were also made by Professor Hubert Chanson, an expert in dam and reservoir engineering with extensive firsthand knowledge of the Wivenhoe system, that mismanagement of the Wivenhoe Dam might be a contributor to the some flooding in the lower Brisbane valley. While an expert engineer, Michael O'Brien—a senior manager of an ASX-listed resources company and an outside consultant evaluating cause—agrees that "massive releases of water from Wivenhoe Dam on Tuesday, January 11, did indeed produce most of the flooding in the Brisbane River the following afternoon, with a peak in the early hours of Thursday morning, January 13. The dam's releases into the Brisbane River also caused the Bremer River, which winds through the city of Ipswich, and the Lockyer Creek to back up and cause much of the flooding outside Brisbane." This was corroborated by a panel of engineers hired by Insurance Council of Australia. O'Brien also found that the Wivenhoe Dam and Somerset Dam did not hold the maximum capacity they were capable of holding during the crisis period, which would have significantly alleviated flooding. Only one source, Neal Ashkanasy, who specialises in social and organisational psychology (and 35 years ago was involved in the design of Wivenhoe Dam), found fault with these results and instead finds that the dam was operated correctly throughout the time of the storm and the flood that followed, saying the "dam was run with outstanding precision."
  Isolated flooding started across parts of the state in early December. On 23 December, a monsoonal trough crossed the coast from the Coral Sea, bringing torrential rain that fell in a broad swath from the Gulf of Carpentaria to the Gold Coast. The widest range of intense rainfall occurred on 27 December (with very high daily totals recorded on 25 December, near where Cyclone Tasha crossed the coast). By 30 December vast areas of Southern and Central Queensland were affected by the flood. The conditions led to a large influx of snakes in the Rockhampton area, as well as some crocodiles.
caption: track of Cyclone Tasha
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