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Coastal lagoons
The Central Coast’s four coastal lagoon systems (Wamberal Terrigal Avoca and Cockrone) are a significant geographic feature of the region.

The Central Coast’s four coastal lagoon systems (Wamberal, Terrigal, Avoca and Cockrone) are a significant geographic feature of the region. They are a highly valued natural resource and support a network of significant ecological communities as well as a diverse range of recreational uses. 

These lagoons belong to a special class of estuary known as Intermittently Closing and Opening Lakes and Lagoons (ICOLLs). An ICOLL is a shallow coastal water body with an entrance barrier connected at least intermittently to the ocean by one or more restricted inlets.

They have a low tolerance of external pressures compared to other estuary types, so they need to be carefully managed and conserved in order to prevent significant environmental degradation. However, past land-use changes and human activities combined with a growing population are placing increasing pressure on the natural values and ecological health of the lagoons.

Improved planning aims to provide a balance between environmental protection and human activities. Council is working on a range of planning activities which aim to provide a balanced long-term strategic management framework for the integrated and ecologically sustainable use of our coast and estuaries.

Coastal Lagoons water levels and intervention triggers

There are four lagoons on the Central Coast which discharge directly into the Pacific Ocean -Avoca, Cockrone, Terrigal and Wamberal.  

The lagoons are characterised by sand berms that naturally control the entrance conditions.

Council intervenes to open these lagoons when water levels reach a trigger level (as listed in table below), and when the lagoons are closed to reduce the risk of flooding. This is a similar approach to that taken in other coastal local government areas.

Council owns water level gauges at each of these lagoons, and current levels can be viewed from links in the table below.

The Flood Planning Level is the minimum floor level for any new residential developments. 

Avoca Lagoon

View: Live water level, Avoca Lagoon

  • Trigger Level for Mechanical Opening: 2.09m AHD
  • 1 in 100 chance flood level: 3.00m AHD
  • Flood planning level: 3.70m AHD

Cockrone Lagoon

View: Live water level, Cockrone Lagoon

  • Trigger Level for Mechanical Opening: 2.53m AHD
  • 1 in 100 chance flood level: 3.62m AHD
  • Flood planning level: 4.30m AHD

Terrigal Lagoon

View: Live water level, Terrigal Lagoon

  • Trigger Level for Mechanical Opening: 1.23m AHD
  • 1 in 100 chance flood level: 2.48m AHD
  • Flood planning level: 3.40m AHD

Wamberal Lagoon

View: Live water level, Wamberal Lagoon

  • Trigger Level for Mechanical Opening: 2.40m AHD
  • 1 in 100 chance flood level: 2.94m AHD
  • Flood planning level: 3.60m AHD
  • Council uses the latest scientific information, combined with community and stakeholder feedback, to develop Coastal Zone Management Plans (CZMPs).

    The primary purpose of a CZMP is to describe what can be done by Council, other public authorities and the community, to address priority management issues over a defined implementation period. These issues include:

    • pressures on coastal ecosystems
    • community uses of the coastal zone, and
    • managing risks to public safety and built assets.
  • The major elements of the revised CZMP for the Central Coast’s Coastal Lagoons focus upon improving water quality through catchment management, review of Council's lagoon entrance management practices, vegetation enhancement and sustainable recreational usage of the lagoon and surroundings.

    Coastal Zone Management Plan for Gosford Lagoons 2015

  • The Wamberal, Terrigal, Avoca and Cockrone coastal lagoons have natural and acquired similarities and differences. Human influences include the developed land within catchments, modification of foreshore areas, along with artificial opening of lagoon entrances to mitigate flooding of low-lying foreshore areas. These influences have placed different levels of pressure upon the lagoons, with commensurate impact on their health and condition. The Study guides Council and the community to appropriately manage activities in and around the lagoons, guide conservation and rehabilitation efforts.

    Coastal Zone Management Study for Gosford Lagoons 2014
    Coastal Lagoons Processes Study 2010

    After completing the Gosford Lagoons Data Compilation Study in April 2008, Council engaged consultants to undertake the Gosford Coastal Lagoons Processes Study. This was the next step in the revision of the 1995 Plan.

    The Processes Study identifies enhancement, development and management needs to ensure the long-term ecological sustainability of the lagoons. It provides a comprehensive report on the existing physical, chemical and biological condition of the lagoons. It also documents processes and interactions that influence the condition of the four coastal lagoons.

    The objectives of the processes study were to:

    Identify and document the physical and chemical functioning of the Lagoons as well as related processes. These include:
    a) Hydrodynamic: tidal behaviour, freshwater inputs, water balance, mixing, exchange with the Tasman Sea.

    b) Sedimentary processes: catchment geology and geomorphological characteristics, sediment movement, sedimentation rates, and sediment types and entrance stability.

    c) Interactions between these processes - establishment of the water quality parameters (physical, chemical and biological) important to the health of the lagoons, evaluation of mixing and flushing of pollutants, preparation of a nutrient budget.

    • Identify and document the biological functioning of the lagoons and related processes covering flora and fauna, species composition and distribution; the productivity and health of the ecosystems; the range and sensitivity of habitats; and rare and endangered species.
    • Define baseline conditions of the estuarine processes and interactions on which management decisions can be made.
    • Review the existing and strategic land use activities that may potentially impact upon the management needs of the lagoons.

    Undertake any further data collection or monitoring to aid the subsequent stages of an estuary management study and formulating an estuary management plan for the lagoons.

    Gosford Coastal Lagoons Processes Study - Volume 1 - Main Report and Figures

    Gosford Coastal Lagoons Processes Study - Volume 2 - Appendices

  • Pearl Beach Lagoon is a special landscape feature with ecological and localised visual significance in an area that does not have any other alternative substitute for the role that the lagoon plays in the local ecosystem. The lagoon is an example of the small enclosed saline coastal lagoons which occur along the coast of south-eastern Australia.

    Since urban development, the habitat value of the lagoon has declined because of pressures from urban development (e.g. run-off, vegetation loss, weed infestation) and modifications to the natural movement of water (e.g. the weir, drainage channels, groundwater extraction). These issues are likely to be exacerbated into the future as a result of population increase, climate change impacts and the cumulative effects of past practices.

    The condition of the wetland and its preservation are of concern. With an improved understanding of the lagoon system, Council worked with the community to develop the Pearl Beach Lagoon Coastal Zone Management Plan.

    Pearl Beach Lagoon Condition Study and Community Uses Report

    Coastal Zone Management Plan for Pearl Beach Lagoon 2014

    Council is now working with the Pearl Beach Progress Association to identify opportunities to implement actions.

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