Yeramba Lagoon restoration

Yeramba Lagoon is located on the left bank of the Georges River estuary, approximately 20 km upstream from Botany Bay. Historically, the lagoon was connected to the estuary, receiving tidal flows, and was populated by macrophytes including mangroves, saltmarsh, and freshwater swamp species. Following on from years of reclamation, construction and poor land management have led to an accumulation of contaminants and poor tidal flushing.

The lagoon is managed by NSW National Parks & Wildlife Service, who sought to restore tidal flushing and re-create the lost critical blue carbon coastal wetland ecosystem. WRL completed a detailed investigation of the lagoon condition and hydrology, to develop a restoration action plan. 

The construction of Henry Lawson Drive in the early 1940s had resulted in the reclamation of much of the lagoon entrance, with flow connection maintained beneath the roadway. Additional road development in the 1960s including the construction of an elevated weir structure (above high tide level) prohibited tidal exchange and promoted the retention of freshwater.

Yeramba Lagoon, before and after restoration. Image credit: NearmapPoor tidal flushing and catchment runoff had resulted in the accumulation of contaminants with high nutrient concentrations. These conditions led to the proliferation of invasive aquatic freshwater weeds. Annual herbicide application prior to 2010 had reduced the weed biomass, however limited maintenance since 2010 had resulted in the growth of weeds to such a significant density that no open water was present. A floating layer of organic matter approximately 40 cm thick formed, which supported a dense community of small shrubs (1 to 2 m in height).

Following the restoration plan, three hectares of weeds have been manually removed, and in late-2020 the historic weir structure was also removed, with modern infrastructure installed in its place, enabling adaptive management of the site into the future. Daily tidal flushing was restored to the lower half of the lagoon, with areas above the high tide level being populated by freshwater wetland vegetation species.

It is expected that mangrove and saltmarsh species will re-establish across tidal areas of the lagoon in the near future, further expanding key fish habitat within the Georges River estuary and restoring the blue carbon coastal wetland ecosystem.

Water level monitoring data

Salinity monitoring data

Site camera

DPI Recreational Fishing Trusts

Acknowledgements

 

Funding to implement the restoration plan was provided by the Commonwealth Department of Agriculture, Water and the Environment, and by NSW DPI Fisheries’ Recreational Fishing Saltwater Trust’s “Flagship Habitat Action Grant Program”.

 


Disclaimer

Please note that data presented on this page includes real-time measurements sent directly from field stations. Subsequently, this data has not been quality controlled and may contain errors. Please contact WRL directly should you have any queries regarding this data and the suitability of its use.


For further information, contact:

Duncan Rayner | Director, Industry Research (acting) | d.rayner@wrl.unsw.edu.au

Barry Hodgson | NPWS Ranger | Barry.Hodgson@environment.nsw.gov.au