9.9.5 Types of floods Although Australia is the driest inhabited continent, it still experiences heavy rainfall and floods. These floods can cause: • damage to property • loss of livestock • loss of human life. In some cases, entire parts of towns have been destroyed. For example, in 1852, one-third of the town of Gundagai was washed away.
SkillBuilder discussion Geographical inquiry 1. How does the image show Rockhampton before and after the flood? 2. What changes are visible in the river and surrounding areas after the flood? 3. How might the flood have impacted Rockhampton’s people and buildings?
FIGURE7 How did the floods affect Rockhampton? Rockhampton ( a ) before the 2011 flood and ( b ) after the flood
(a)
(b)
There are three main types of floods. 1. Slow-onset floods • Happen along inland river floodplains and can last for weeks or months. • Are caused by heavy rain and run-off upstream. • It can take days or weeks to affect farms and towns downstream. 2. Rapid-onset floods • Occur in mountain headwaters of larger inland rivers or rivers flowing to the coast. • The water flows faster due to steep rivers, leaving less time to prepare. • Are often more damaging. 3. Flash floods • Are caused by short but heavy rainfall, such as during a severe thunderstorm. • They are the most dangerous, with high risks to property and life because they happen quickly. • Are a major problem in cities with poor drainage systems. 9.9.6 The Queensland floods, 2011 and 2022 In both 2011 and 2022, Brisbane experienced catastrophic flooding. Table 1 provides a summary of the causes of these events and Table 2 compares their impact. In 2011, the operators of the Wivenhoe Dam were criticised for their management of the dam allowing its water level to rise to near capacity before releasing water. Earlier release may have reduced the impact of flooding as the release would have been controlled over a longer period of time. However, as the dam was close to capacity, with more rain on the way, larger volumes had to be released at once, during the peak of the flood.
302 Jacaranda Humanities Alive 7 Victorian Curriculum Third Edition
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