Broadly speaking, an estuary is a semi-enclosed coastal body of water where:
- salt from the open sea mixes with freshwater draining from the land
- where waters with different salinities mix or
- where marine and fluvial sediments occur together.
The estuaries included in this assessment were selected according to management interest rather than a strict scientific definition.
Estuary Assessment 2000 assessed the condition of 979 estuaries and classified each estuary by the key geomorphological processes driving it.
Geosciences Australia developed a process-based classification covering physical forces (wave, tide and river energies) driving the form and function of Australian estuaries. Geomorphic characteristics and sedimentary environments have been mapped for 405 of Australia's modified coastal waterways.
The assessment was done in two stages.
- Stage 1: Identification of Australia's near-pristine estuaries based on expert opinion through State-based workshops.
- Stage 2: Determining the extent of change for those estuaries no longer considered to be in near-pristine condition through a more quantitative condition assessment based on a pressure-state-response model.
Australian estuaries were found to be:
- 50% near pristine
- 22% largely unmodified
- 17% modified
- 11% severely modified
An estuary was classified as near-pristine if it had:
- a high proportion of natural vegetation cover in the catchment
- minimal changes to hydrology in the catchment
- no changes to the tidal regime
- minimal disturbance from catchment land use
- minimal changes to floodplain and estuary ecology
- low impact human use of the estuary
- minimal impacts from pests or weeds
The other three categories of the assessment were used to indicate increasing levels of change for some or all of these criteria.
For more information on the assessment and findings, go to the Understanding Estuary Condition section.
Use the sub-region navigation menu above to go to a state or basin for detailed assessment information about estuaries in that region. Below is a map of basins to help with navigation. Larger maps are provided at the state level.
Estuary Assessment 2000 has been undertaken by the Geosciences Australia, Commonwealth Scientific and Industrial Research Organisation (CSIRO) and University of Queensland (UQ) as partners of the Cooperative Research Centre for Coastal Zone, Estuary and Waterway Management (Coastal CRC) in association with the Department of the Environment and Heritage (State of the Environment Reporting), Fisheries Research and Development Corporation (FRDC) and States and Territories.
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