Floods are not always caused by heavy rainfall. Flooding can also be caused by:
- Seawater Flooding (after a cyclone or severe storm).
- Tidal Flooding (Floods caused by high tides from higher than normal river water levels).
- Run off from rivers and dams (eg, following a snow melt or when dams start to overflow).
- Urban drainage. (When city drainage systems fail, people can be caught in stormwater drains, trapped in their cars, or even swept off roads by water).
Floods are not always devastating. Often they are welcome relief for areas suffering drought. They are a natural way for wetlands, and native waterways to survive. Soils with high salt levels can also benefit from flooding.
Types of Floods in Australia
Inland rivers in the vast flat areas of Western Australia, central/western New South Wales and Queensland can often flood. These floods may take days to build-up. They can last for one or more weeks and can even last for months on some occasions.
The damage caused by floods in these areas can lead to major losses of livestock, cutting off rural towns and damaging crops, major roads and railways.
As the name suggests, rapid-onset flooding happens more quickly than slow-onset floods. These floods can potentially be much more damaging and can pose a greater risk to loss of life and property because there’s generally much less time to take preventative action, and the flow of water is faster and more dangerous. This type of flooding can affect most of our major towns and cities.
Flash flooding results from short, intense bursts of rainfall, often from thunderstorms. It can occur in almost all parts of Australia and poses the greatest threat of loss of life. People are often swept away after entering floodwaters on foot or in vehicles. These floods can result in significant property damage and major social disruption. They are more serious in urban areas where drainage systems are often unable to cope.