Floods are one of the deadliest natural disasters in Australia.
We issue flood watches and warnings to help keep Australians safe.
Understanding flood and how we warn you about it could save your life.
1. Even minor floods can be dangerous
Floods don't have to be major to be hazardous. Even minor flooding, which leaves low-lying areas inundated and leads to road closures, has serious risks. Floodwater can:
- have surprisingly strong currents that can sweep people off their feet
- contain sewage, debris or other contaminants from locations far beyond where you can see
- be much deeper than it looks.
Video: Understanding flood classifications
Riverine floods typically occur 6 or more hours after heavy rainfall. In Australia, we have 3 riverine flood classifications: minor, moderate and major.
Minor flooding refers to inundation of low-lying areas next to watercourses. Minor roads may be closed and low-level bridges submerged. In urban areas inundation may affect some backyards and buildings below the floor level as well as bicycle and pedestrian paths.
For moderate flooding the area of inundation is more substantial. Main traffic routes may be covered and some buildings may be affected above floor level. Evacuation of flood affected areas and removal of stock may be required.
Finally, major flooding can be very dangerous and may result in extensive inundation of rural and urban areas. Properties and towns are likely to be isolated and major traffic routes and rail routes are likely to be closed. Evacuation of people from flood affected areas may be required and utility services may be impacted.
The Bureau produces warnings and advice to local communities who are experiencing, or are at risk of experiencing riverine flooding.
Flood Watches provide early advice of a developing situation that may lead to flooding. While Flood Warnings are issued when floods are likely to occur or are already occurring.
Sometimes short bursts of heavy rainfall can lead to rapid onset flooding, known as flash flooding. When this is likely to occur, the Bureau will issue a severe weather warning for heavy rain that may lead to flash flooding.
Current flood watches and warnings, as well as severe weather warnings can be found on our warnings page or the BOM weather app. You can also access rainfall and river level data for around 3,500 locations across Australia.
Sadly, fatalities are common around flood waters. Just 15 cm of water is enough to make your car float. So remember, the best way for you to stay safe is to stay out of flood water and follow advice from local emergency services.
2. There are 2 types of flood
Floods are defined as flash or riverine.
Flash floods happen quickly – within 6 hours of rain falling. They usually affect a localised area. They often happen:
- after short bursts of heavy rain, such as from a thunderstorm
- where the ground is already saturated.
Riverine flooding is when rivers break their banks. It's often caused by heavy rain but can also be caused by:
- king tides and storm surge
- dam releases
- snowmelt.
3. Floods can happen weeks or months after rain
Australia has many long rivers. Flood water from rain that fell hundreds of kilometres upriver takes time to flow down and affect other locations.
In parts of inland Australia, riverine flooding can affect thousands of square kilometres for long periods of time.
4. Planning early can save lives and property
Floods can happen quickly – potentially causing massive damage and taking you by surprise. They can also cut off communication and power, and disrupt transport.
- Ask – find out if floods have affected your neighbourhood before, and what your risks are.
- Learn – understand the different types of flood and what warning is available for each – and check with your local council if there's a flash flood warning service for your area.
- Plan and prepare – especially if your local area has a history of flooding, then prepare a flood action plan, evacuation plan and a preparation checklist.
For more information on preparing for a flood, contact your state or territory emergency services.
5. Flood watches and warnings alert you to danger
Flood watches provide early advice of developing weather that could lead to flooding. Flood warnings let you know when flooding is likely or is already happening.
You can see any active flood watches or warnings on our Warnings and alerts page or through the BOM Weather app.
