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Home > Coastal and floodplains > Estuaries

Estuaries in NSW

What are estuaries?

An estuary is a partially enclosed coastal body of water ... part sea ... part waterway ... part land, a place of transition from salt water to fresh water, from tidal to non-tidal, and from wet to dry.

Estuaries come in all shapes and sizes and go by many different names, such as bays, lakes, lagoons, harbours, rivers or inlets. Some well-known examples in NSW include Sydney Harbour, Botany Bay, Port Stephens, Lake Macquarie, and the tidal sections of coastal rivers such as the Clarence, Richmond, Hawkesbury and Tweed. Tourism, fishing, and other commercial activities thrive on the wealth of natural resources estuaries supply. For example commercial fishing is worth some $80 million per year, with recreational fishing estimated to be worth $500 million per year. The building industry sources sand and gravel from estuary areas worth over $100 million per year. The protected coastal waters of estuaries also support important public infrastructure, serving as harbours and ports vital for shipping, transportation, and industry.

It is therefore important we protect and sustainably manage our estuaries, both for environmental and economic reasons. They provide a wide range of unique ecosystems where the conditions are constantly changing as the tide ebbs and flows each day.

There are many different habitat types in estuaries, including:

• Mangroves and salt marshes
• Sea grasses and open waters
• Inter-tidal mud flats and mud basins
• Sandy shoals and beaches
• Rocky shores and reefs; and
• Fresh water wetlands and floodplains.

The productivity and variety of estuarine habitats foster a diversity of wildlife, including shore birds, fish, prawns, crabs, oysters and other shellfish, marine worms, marine mammals and reptiles. These animals are linked to one another and an assortment of specialised plants, algae and microscopic organisms, through complex food webs and other interactions.

Besides serving as important habitat for wildlife, the wetlands that fringe many estuaries also perform other valuable services. Water draining from the catchment carries sediments, nutrients, and other pollutants. As the water flows through the marshes, much of the sediments and pollutants are filtered out. This filtration process creates cleaner and clearer water, which benefits both people and marine life.

Wetland plants and soils also act as a natural buffer between the land and ocean, absorbing flood waters and dissipating storm surges. This protects land based organisms as well as valuable real estate from storm and flood damage. Salt marsh grasses, mangroves and other estuarine plants also help prevent erosion and stabilise the shoreline.