Estuary Management Planning St Georges Basin - 2004

 

 

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Indicator description

St Georges Basin

Environmental Overview

Environmental Issues

Environmental Pressures

Estuary Management Programs

UoW Environmental Science Research Projects

Environmental Overview 

St Georges Basin is relatively large, covering an area of 40 sq km, with a catchment of 350 sq km.  Most of the catchment is zoned for rural use and over 80% is forested.  There are no recorded periods of closure for the Basin. 

The waters of St Georges Basin have limited exchange with the ocean and are drawn from large catchment, which gives it a high trapping efficiency with significant potential for nutrient overload.  Human derived inputs, therefore, need to be carefully managed to avoid this situation (Reference: Murray, E. Smith, C., Haese., R. and Heggie., D. 2004. St Georges Basin Nutrient Survey - Results Summary For Shoalhaven City Council. Geoscience Australia, 2004. To obtain further details of this report contact Council's Natural Resources & Floodplain Section).

Residential population of the townships within the catchment was around 16,000 in 2001, with holiday population being up to 5 times greater.  All towns within the St Georges Basin catchment are sewered.

Environmental attributes

  • Diverse aquatic habitats, including large areas of seagrasses, mangroves, saltmarshes and freshwater wetlands.  Sixteen wetlands around the lake are protected under Coastal Wetlands State Environmental Planning Policy No 14.;

  • Largely unmodified southern shoreline;

  • Diversity of aquatic flora and fauna;

  • Availability of a variety of high quality recreational activities; and

  • A high level of visual amenity.

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Environmental Issues

  • Catchment runoff entering the Basin carries nutrients and sediments which may affect the overall water quality of the Basin.  There is concern regarding the affect of sediment and nutrient input on seagrasses;

  • Nutrient accumulation in the muddy sediments of the Basin may threaten flora and fauna diversity and abundance. (Reference: Murray, E. Smith, C., Haese., R. and Heggie., D. 2004. St Georges Basin Nutrient Survey - Results Summary For Shoalhaven City Council. Geoscience Australia, 2004. To obtain further details of this report contact Council's Natural Resources & Floodplain Section);

  • The Basin suffers from some localised bank erosion and siltation.  This may be associated with collapsing banks in the canal estates near the Basin mouth, creek bank denudation of some tributaries, erosion from inappropriate power boat usage and the formation.  Informal picnic / boat parking areas along banks create areas susceptible to erosion by flood flows and boat wash.  There appears to be some sediment deposition around stormwater drainage outlets;

  • Erosion along Sussex Inlet is causing a loss of foreshore vegetation;

  • Concern exists regarding the potential impact of fishing on the ecology of the Basin, particularly on the seagrasses of the Basin.  The Basin has now been declared a recreational fishing reserve, excluding commercial fishing;

  • The visual qualities of the area have been harmed by unauthorized clearing and destruction of native vegetation; and

  • Development pressure adjacent to the estuary has the capacity to add a high pollutant load to the waterway.

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Environmental Pressures

  • Public access to viewing areas around the Basin is restricted.  Future development has the potential to further impact visual amenity;

  • Continuing urban expansion into wetland areas and forested foreshores may compromise their integrity as intact ecosystems and impact on the Basin’s ecology;

  • Aboriginal archaeological sites are frequently located along waterways and coastal sites.  There is, therefore, potential for degradation from any future development at such locations;

  • There is potential for increased erosion from development, recreation and agriculture.  An increase in sediment and nutrient export from new developments can impact upon water quality;

  • Any degradation in water quality may lead to degradation of the estuary’s ecology, diminished visual and aesthetic appeal and recreational appeal.  Additionally there would be potential for an impact on local industry through smaller fish catches, declining tourism etc;

  • Recreational fishing is undertaken within the lake.  There is potential for a decline in fish and prawn diversity and abundance if fishing is not managed;

  • Recreational and boating activities within the catchment can impact on foreshore stability and bird habitat quality.  Informal boat launching sites may decrease bank stability and may harm aquatic vegetation and its associated ecological community;

  • Tourism and recreational lake usage have the potential to impact upon such things as habitat and flora and fauna abundance;

  • Introduced animals, including foxes, domestic and feral cats and dogs, black rats and rabbits, threaten native animal and plant populations;

  • Weeds, although scarce overall, are prevalent in some areas where they threaten native plants.  Native vegetation is often located adjacent to towns and in water courses and may be impacted on by stormwater flows carrying weed seed etc. from urban areas;

  • Dumping of garden refuse and other material causes damage to bushland and continues to be an issue; and

  • There is some clearance of and damage to vegetation on foreshores and other areas.

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Estuary Management Programs

Key implementation actions in progress or completed in partnership with Shoalhaven City Council and Department of Infrastructure, Planning and Natural Resources (DIPNR) and funded under the following programs include:

Estuary Program

  • 2002: Northern Shoreline Erosion Study completed $20,000;

  • 2002: Stormwater Management Plan Review completed as pilot study;

  • 2002-2003 Stormwater Management Plan Implementation Stage 1 completed;

  • 2002-2004 Erosion Remediation Project design- John Williams Reserve, Paradise Beach, Home Bay, Pats Bay;

  • 2003-2004 implementation of Bushfire Asset Protection Zones for the villages;

  • Geoscience Australia: nutrient balance study (Reference: Murray, E. Smith, C., Haese., R. and Heggie., D. 2004. St Georges Basin Nutrient Survey - Results Summary For Shoalhaven City Council. Geoscience Australia, 2004. To obtain further details of this report contact Council's Natural Resources & Floodplain Section);

  • 2004-2005 Erosion Remediation projects implementation $90,000;

  • 2003-2004 Sussex Inlet Channel: erosion remediation design $20,000; and

  • 2004 Caulerpa outbreak discovered and treatment commenced. See NSW Fisheries website for more information http://www.fisheries.nsw.gov.au

Flood Program

  • 2004 Flood plain Management Plan completed.

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University of Wollongong Environmental Science Research Projects

  • Shallow water seagrass fish communities of Intermittently Open and Closed Lakes and Lagoons (ICOLLs) of southeastern  Australia.  Author:  Martine Jones

To obtain a full copy of this report or more information contact Environmental Science, University of Wollongong.

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Surface Water Quality St Georges Basin

 

Home | Water | Coast and Estuaries | St Georges Basin | 2004