Where do Floods occur?

A road completely cut off and a transport truck partially submerged in flood waters

Severe flooding on roads
Reproduced with permission from EMA

Riverine flooding occurs in relatively low-lying areas adjacent to streams and rivers. In the extensive flat inland regions of Australia, floods may spread over thousands of square kilometres and last several weeks, with flood warnings sometimes issued months in advance. In the mountain and coastal regions of Australia flooding can happen rapidly with a warning of only a few hours in some cases.

The Great Dividing Range which extends along the length of eastern Australia provides a natural separation between the longer and slower westerly flowing rivers and the shorter, faster easterly flowing coastal rivers. In some cases natural blockages at river mouths, including storm surge and high tides, may also cause localised flooding of estuaries and coastal lake systems.

Flash floods can occur almost anywhere there is a relatively short intense burst of rainfall such as during a thunderstorm. As a result of these events the drainage system has insufficient capacity or time to cope with the downpour. Although flash floods are generally localised, they pose a significant threat because of their unpredictability and normally short duration.

The Bureau of Meteorology maintains the Australia Rainfall and River Conditions which contains up-to-date rainfall and river information for all catchments within Australia.

Interesting fact: The floods following cyclone Wanda in Brisbane in January 1974 resulted in 16 deaths and 300 injuries, made 9,000 people homeless. An area which has not been flooded in the past is not excluded from possibly flooding in the future.