Basically, it means a large amount of water overflowing beyond its normal limits over dry land.
The Federal Government's legal definition of flood is 'the covering of normally dry land by water that has escaped or been released from the normal confines of any lake, river, creek or other natural watercourse, whether or not altered or modified; or any reservoir, canal or dam.'
It doesn't mean
- Heavy downpours of rain (unless they actually cause a 'flood')
- Sea or ocean movements (such as storm surges, high tides or wave action)
- Tsunamis (which may be covered as 'earthquakes')