The creeks and rivers in Australia form a drainage system. Eventually, all rivers lead to the sea, or to large inland depressions such as Lake Eyre. Floods occur when river systems are unable to cope with unusually high rainfall or melting snow. There are three main types of floods in Australia: mountain/coastal floods, flash floods, and inland floods.

Mountain and coastal floods occur in hilly or mountainous areas, especially near the east coast of Australia along the Great Dividing Range. The rivers in this area are short but relatively steep, causing fast-flowing flood waters which often rise quickly before emergency measures can be taken. Floods usually last only two or three days.

Flash floods are usually caused by sudden downpours from thunderstorms and affect small areas. They can cause great damage in towns and cities where networks of storm water drains may...