Flash flooding is defined by the Bureau of Meteorology as flooding in which less than six hours warning time is available. This is often the case with riverine flooding in short and/or steep creeks and rivers and is always the case with overland flows.
When intense rain is expected in these types of catchments the Bureau usually issues a generalised flood warning or may issue a Severe Weather Warning with the warning that flash flooding may occur.
Because flash flooding is generally caused by short bursts of intense rainfall it is difficult to predict precisely where it will occur so flash flood warnings or generalised flood warnings will be issued for regions. Although there are flash flood warning systems for some larger urban creeks, there is only sufficient time to warn that significant amount of rain has fallen to cause a flood, and not enough time to predict how large the flood will be.