About our flood warning services

Flood warning services

We provide flood forecasting and warning services in each Australian state and territory as part of the Total Flood Warning System. Our partners in this system include:

  • emergency management agencies
  • government departments with responsibility for water management
  • water authorities
  • local councils.

National Arrangements for Flood Forecasting and Warning outlines the roles and responsibilities of each level of government. It also describes the arrangements and agency roles that apply in each jurisdiction.

The Total Flood Warning System involves information flowing between ourselves, councils, dam operators and water agencies. This is used by emergency management agencies to make decisions and in community response.

There are many aspects to flood forecasting and warning. These include weather observations, dam operator information, modelling likely scenarios, decision-making and response.

We're responsible for monitoring and predicting a flood. We also work closely with state and territory governments, local councils and state emergency services (SES) to interpret the data and communicate the key messages to the community.

In this process, we could issue a Flood Watch or a Flood Warning.

Graphic summarising the attributes of flood watches and warnings, as explained in the text below

Flood Watch

We issue a Flood Watch when forecast rainfall suggests that local and riverine flooding is possible. Its purpose is to provide early advice of a developing situation that may lead to flooding. A Flood Watch isn't a warning of imminent flooding.

A Flood Watch provides information about a developing weather situation including forecast rainfall totals and catchments at risk of flooding. It can also indicate how severe a possible flood might be. It provides links to weather warnings, other flood-related information, and contact details of relevant emergency services.

A Flood Watch can be issued up to four days in advance of expected flooding. They are updated at least daily and finalised once all areas are covered by Flood Warnings or the risk of flooding has passed.

If a Flood Watch is issued for your area, look out for future updates and possible Flood Warnings. Follow the advice of your local emergency services. If flooding develops, consider moving livestock, family and possessions to higher ground.

The Flood Watch service covers the whole country. Flood Watch areas are defined and reviewed in partnership with key agencies in each state and territory to ensure they are locally relevant.

View the Flood Watch area for your region:

Flood Warning

We issue a Flood Warning when we're more certain that flooding is expected at a particular location. Flood Warnings are more targeted and are issued for specific catchments and locations within catchments. We forecast how severe the flood is expected to be in each Flood Warning.

Flood Warnings typically include predictions about the level we expect the river to rise to. Where less data are available, Flood Warnings may include a statement about future flooding that is more general. For example, 'River levels are elevated along the Coal River around Richmond and are expected to remain elevated into Wednesday'. The type of information we provide depends on the:

  • quality of real-time rainfall and river-level data available
  • capability of rainfall and hydrological forecast models
  • level of service agreed with partner organisations.

When there are insufficient data to make specific predictions, or in the developing stages of a flood, we provide generalised flood warnings. These are based on forecast rainfall and knowledge of historical flood response. Generalised warnings advise that flooding is expected in particular river valleys but don't provide information about how severe the flood may be or precise locations.

In the case of flash floods our response is different, and the best warning advice comes in the form of a Severe Weather Warning. Our flood warnings cover larger rivers that take more than six hours to respond to rainfall. The reason they're treated differently is because the longer lead time enables a different response. We can work with our government partners to collect data, run prediction models, interpret flood mapping and determine potential consequences, as well as issue and communicate warnings. Flash floods typically happen so quickly that there isn't time to run these processes.

While we don't warn for flash floods, we do provide forecasts and warnings for severe weather conditions and potential heavy rainfall that can cause flash flooding.

Flood classifications

The emergency services use a three-tiered scheme that classifies flooding as minor, moderate or major at key river height stations. Classification levels at each station are decided by local community and SES. They're defined by the water level that causes certain impacts.


Transcript

Minor flooding

If the water level reaches the minor flood level, it causes inconvenience. Low-lying areas next to water courses are inundated. Minor roads may be closed and low-level bridges submerged. In urban areas flooding may affect some backyards and buildings below floor level as well as bicycle and pedestrian paths. In rural areas removal of livestock and equipment may be required.

Moderate flooding

If the water level reaches the moderate flood level, the area of inundation is larger. Main traffic routes may be affected. Some buildings may be affected above floor level. Evacuation may be required. In rural areas removal of livestock is necessary.

Major flooding

If the water level reaches the major flood level large areas are inundated. Many buildings may be affected above floor level. Properties and towns are likely to be isolated and major rail and traffic routes closed. Evacuation may be required. Utility services may be affected.

River heights

You'll see these terms used to describe river heights in our Flood Warnings. River heights are measured in metres.

Observed river height
This is the depth of water at a river height measuring gauge. In most cases, observed river height is measured relative to a local reference point. For example, a typical river height might be 'the South Esk River at Llewellyn in Tasmania, is at 1.60 metres'. In many tidal areas, as well as a few inland areas, river levels are expressed in metres above sea level or Australian Height Datum (AHD).

Peak river height
This is the highest river height observed during a flood event at the specified site on the river.
You can view a river's observed height over time through our Australia Rainfall and River Conditions page. This chart shows the level of the South Esk River at Llewellyn during a flood in August 2020. The highest water level (peak river height) was observed to be 6.11 m at 2 pm on Monday 17 August 2020.

Predicted river height
This is the height to which the river is predicted to rise at the gauge referred to in the warning. The actual depth of floodwater will vary across the floodplain. Local councils, emergency services and landowners use the predicted river height to determine which areas are likely to flood. They use their knowledge of past flood events and estimates from flood studies to assess this. The accuracy of river height predictions depends on various factors, including the type of flood forecasting model and its input data. Predicted river heights are regularly updated as more information becomes available.