TABLE1 Causes of the 2011 and 2022 floods
Causes of the 2011 floods
Causes of the 2022 floods
Unseasonal rain
Heavy rainfall spring rains linked to the monsoon season An unusually strong La Niña event that increased rainfall caused rivers to burst their banks Tropical Cyclone Tasha in December 2010 fed more water into already overflowing river systems Prior to the heavy rainfall, Wivenhoe was sitting at just 40% capacity Heavy rainfall and run-off exceeded the dam’s capacity — the equivalent of 191% of its capacity The spillway had to be opened to prevent the dam overflowing, adding to the flooding in Brisbane
A low-pressure system over Queensland’s southern coast drew moisture from the Coral Sea creating intense rainfall As the system moved south it turned into an East Coast Low, leading to more rain Prior to the heavy rainfall, Wivenhoe was sitting at 58.7% capacity Heavy rainfall over three days would have raised the dam’s water level to 183.9% of its capacity The spillway had to be opened to prevent the dam overflowing, adding to the flooding in Brisbane
Wivenhoe Dam — Brisbane’s major water source
TABLE2 Comparing Brisbane’s floods 2011 and 2022 2011
2022
Duration Rainfall
November 2010 – January 2011 Unusually heavy — up to 600 mm in a month in some places
February–May 2022
Record-breaking rainfall in Brisbane – around 800 mm in three days
Deaths
33
13
Damage bill
Estimated $2.38 billion
$7.7 billion
Homes affected
28 000 homes needed rebuilding, and 3572 businesses flooded
More than 23 000 homes and businesses 10 000 km of roads damaged 28% of Queensland rail network affected
Infrastructure damage 19 000 km of roads damaged 28% of Queensland rail network affected
Economic impact
Estimated $6 billion reduction in the economy
Estimated $1.25 billion reduction in the economy
Environmental impact
Wildlife displaced or died due to habitat loss and flooding Contamination of waterways reduced water quality affecting aquatic ecosystems Severe soil erosions impacted natural vegetation and agriculture Destruction of vegetations affected local ecosystems and biodiversity
SkillBuilder discussion Geographical inquiry, Concluding and decision-making
Floods are becoming more common worldwide, causing greater damage to people and the environment. Write one argument supporting and one argument challenging this viewpoint: People should not be allowed to live in flood-prone areas .
TOPIC9 Water in the world 303
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