Australia has an extremely variable climate, and is truly a 'land of droughts and flooding rains'. Throughout Australia's long history, the flood-drought cycle has been a natural part of life, with periods of severe drought followed by extensive flooding playing an important and defining role in shaping the Australian landscape and how we live.

Early Australians typically established settlements on floodplains, along waterways and on coasts, where food and water were plentiful. As a result, floods have had a profound effect on human life and property. As devastating as recent events have been, they are not unique: 77 floods were recorded in Australia in the past 35 years of the 20th century; eight major floods were recorded in Australia in the 19th century; 23 in the 20th century; and six in the first decade of the 21st century.

And nature will undoubtedly continue to surprise us into the future. It is also important to recognise that floods can have some beneficial consequences, for example through replenishing water resources. Most of Australia’s unique flora and fauna have adapted to and depend on flood cycles, relying on the floods to trigger breeding, disperse seed, provide food sources and connect habitats.

In order to reduce the risk of floods to communities, economies and environments into the future, it is important that lessons from past floods, and advancements in knowledge and technology, are effectively communicated and applied.

An important contribution the science and engineering community can make is to help reduce this risk, by minimising the chance that communities and infrastructure will be flooded, and mitigating the negative impacts when floods occur. We know a lot about flood risk: more than 1000 Australian flood studies have been conducted, and scientists and engineers have developed a very sophisticated armoury of methods to forecast and manage floods to reduce risk. However, there is still uncertainty about the many interacting factors that influence such an event, how these factors are changing in time, and the consequences of a flood if it occurs. Moreover, nature is unpredictable, so no matter how detailed and clever our calculations and management strategies may be, there will always be a risk of flood.

Of course, social science and government policy also play pivotal roles in reducing the negative impacts of floods, improving emergency responses and optimising recovery of communities following a flood. Improvements in this regard rely not just on social science research, but also on government leadership and community awareness and engagement. Given the science and engineering outlook here, flood emergency responses and recovery, which are primarily rooted in social science and policy, will not be addressed.

This report concentrates on floods caused by rainfall and on three key themes to understanding floods. The three themes are floods and their consequences, flood forecasts and warnings, and managing floods. The following paragraphs expand on these three themes, pose the questions we have sought to respond to, and summarise the answers.

References and further reading