Australian Water Information Dictionary

Water forecasts: Flood warning services

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AHD

Australian Height Datum

The datum that sets mean sea level as zero elevation. Mean sea level was determined from observations recorded by 30 tide gauges around the coast of the Australian continent for the period 1966–1968.

See Geoscience Australia for further information.

This definition applies to:

Australian height datum

The datum that sets mean sea level as zero elevation. Mean sea level was determined from observations recorded by 30 tide gauges around the coast of the Australian continent for the period 1966–1968.

See Geoscience Australia for further information.

This definition applies to:

catchment

The land area draining to a point of interest, such as a water storage or monitoring site on a watercourse.

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flash flooding

Flooding occurring within about six hours of rain, usually the result of intense local rain and characterised by rapid rises in water-levels.

This definition applies to:

flood threat advice

An advice of the potential occurrence of flooding inferred from forecast meteorological considerations and an assessment of catchment wetness. The issuing of a flood watch is meant to indicate that vigilance to potential flooding is required of the community.

Related:

Synonym: flood watch

This definition applies to:

flood watch

An advice of the potential occurrence of flooding inferred from forecast meteorological considerations and an assessment of catchment wetness. The issuing of a flood watch is meant to indicate that vigilance to potential flooding is required of the community.

Synonym: flood threat advice

This definition applies to:

local flooding

Describes situations where intense rainfall is expected to cause high run-off volumes in small catchments or localised areas with minimal impact on main streams.

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major flooding

In addition to the criteria for moderate flooding, extensive rural areas and/or urban areas are inundated. Properties and towns are likely to be isolated and major traffic routes likely to be closed. Evacuation of people from flood affected areas may be required.

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minor flooding

Causes inconvenience. Low-lying areas next to watercourses are inundated which may require the removal of stock and equipment. Minor roads may be closed and low-level bridges submerged.

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moderate flooding

In addition to the criteria for minor flooding, the evacuation of some houses may be required. Main traffic routes may be covered. The area of inundation is substantial in rural areas requiring the removal of stock.

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observed river height

The 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.

Related: peak river height

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peak river height

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

Related: observed river height

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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 floodwater 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.

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river alert advice

A river alert is an advice issued whenever specific rainfall or river height criteria are exceeded at key reporting stations.

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river height bulletin

A summary of observed river heights (metres) at selected locations and specified times within river basins. These bulletins are not available in all States.

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watercourse

A river, creek or other natural watercourse (whether modified or not) in which water is contained or flows (whether permanently or from time to time); and includes:

(i) a dam or reservoir that collects water flowing in a watercourse;

(ii) a lake or wetland through which water flows;

(iii) a channel into which the water of a watercourse has been diverted;

(iv) part of a watercourse; and

(v) an estuary through which water flows.

Source: Based on content from the Federal Register of Legislation (https://www.legislation.gov.au/Details/C2018C00505), at 8 Febraury 2019. For the latest information on Australian Government law please go to Federal Register of Legislation

This definition applies to: