How you might be warned about flooding

Namoi River in floodInterpreting flood levels

When the Bureau of Meteorology issue Flood Warnings they contain a predicted flood level. These levels indicate the estimated height of the floodwater.


Flood Levels

Minor flooding

Flooding which causes inconvenience such as closing of minor roads and the submergence of low-level bridges. The lower limit of this class of flooding is the initial flood level at which landholders and/or townspeople begin to be affected in a significant manner that requires the issuing of a public flood warning by the Australian Government Bureau of Meteorology.

Moderate flooding

Flooding which inundates low-lying areas, requiring removal of stock and/or evacuation of some houses. Main traffic routes may be flooded.

Major flooding

Flooding which causes inundation of extensive rural areas, with properties, villages and towns isolated and/or appreciable urban areas flooded. 

Interpreting river heights

Flood Warnings may contain observed, peak or predicted river heights, these are often referenced from a flood gauge at a certain point along a river.

Predicted River Height

The height (in metres) to which the river is predicted to rise at the river gauge referred to in the warning. The actual depth of flood water will vary across the floodplain. Knowledge of past flood events, as well as estimates of flood levels from flood studies, are used by local Councils, emergency services and landowners to determine which areas are likely to be flooded from the predicted river height. The accuracy of this prediction will depend on a number of factors, including the type of flood forecasting model and its input data. Predicted river heights are subject to forecasting error and are regularly updated as more information becomes available.

Observed River Height

Depth of water (in metres) at a river height measuring gauge located along the river. In most cases, a zero reading is the lowest water level that is reached during dry conditions. In many tidal areas, as well as a few inland areas, river levels are expressed in metres above mean sea level or Australian Height Datum (AHD).

Peak River Height

Highest river height (in metres) observed during a flood event at the specified site on the river.



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