What is this project about?
The Kempsey Shire Council area is home to over 70 km of coastline and many coastal waterways (called estuaries).
When it comes to the Shire’s smaller coastal estuaries, an important management issue for Council to consider is how to responsibly manage their ocean entrances. These entrances go through naturally but irregular periods of being open and closed, and the condition of the entrance can sometimes impact on flooding and water quality.
Therefore, Council is in the process of preparing Entrance Management Plans for:
Saltwater Creek and Lagoon
The Entrance Management Plans will lay out a rational decision making procedure for determining if, when and how Council actively manage the state of the entrances.
Who is involved?
The project is initiated by Kempsey Shire Council, and is funded jointly through Council, and the NSW State Government’s Coast and Estuary Grants Program.
The Entrance Management Plans are being developed in partnership with specialist coastal management consultants. It will involve significant engagement with the local community, user groups, and public authorities.
What are ICOLLs?
Many coastal lakes and lagoons alternate between being open or closed to the ocean. These are known as Intermittently Closed and Open Lakes and Lagoons (ICOLLs). About 70 of the coastal lakes and lagoons in NSW are ‘ICOLLs’
Why do ICOLLs change between being open and closed to the ocean?
ICOLLs are separated from the ocean by a sand beach barrier or berm. This entrance barrier forms and breaks down depending on the natural movement of sand in an out of the estuary by waves, tides, flood flows and winds.
Generally speaking, coastal process such as tides and waves tend to push sand into the entrance, while freshwater flows and flood waters from the catchment tend to scour the sand out. The ebb and flow of these forces means that estuaries opens and close to the ocean naturally, in a constant but irregular cycle.
This balance between open and closed states varies for every estuary. Some ICOLLs are nearly constantly open to the ocean, while others can remain closed for several years at a time.
Are closed or open ICOLLs ‘healthier’?
Natural fluctuations between both states are important for the overall health of ICOLL ecosystems. Periods of both flooding and drying are a part of the natural regime, and the flora and fauna that live in ICOLLs natural fluctuation. The ‘healthiest’ option is to leave the ICOLL to operate as naturally as possible.
How are ICOLL entrances managed?
Council is responsible for managing ICOLL entrances and undertaking artificial openings under their duty of care to the local community. The two most common objectives for artificially opening lagoon entrances are () to mitigate flooding, and (ii) to improve water quality.
Entrance management plans can be developed and adopted by Councils to set out relevant rules and procedures, such as for carrying out artificial openings.
Management of ICOLL entrances is sometimes a controversial issue in local communities with competing interests wanting entrances opened more often or less often for different reasons. Developing an entrance management plan therefore requires significant consultation with the local community and a range of public authorities.
What are the impacts of artificially opening ICOLLs to the ocean?
Artificial breaching of ICOLL entrance barriers has been undertaken in many places in NSW in order to alleviate flooding caused by rising ICOLL water levels. Opening up the barrier will cause water to flow from the estuary into the ocean, and can relieve flooding along the ICOLL’s foreshore. While this breaching will occur naturally over time, flooding of low-lying foreshore developments may trigger calls to artificially open an ICOLL before it naturally opens.
While artificial opening may reduce foreshore flooding, the artificial lowering of water levels can cause the death of aquatic vegetation, leading to deoxygenation of the estuary’s water ( blackwater events), which can suffocate fish and result in extensive fish kills.
If an ICOLL is occasionally artificially opened within its natural breakout range ( within the range of water levels a natural breakout would occur) there is unlikely to be any significant environmental impact. However, continual and long-term entrance opening can lead to major environmental shifts of the ICOLL ecosystems.
What are NSW State Government’s Policies on ICOLL management?
The NSW Department of Primary Industries (Fisheries) generally supports minimal interference with ICOLL entrance barriers and advocates natural processes being allowed to operate to the greatest extent possible.
Where can I learn more about ICOLLs and their management?
The NSW Department of Primary Industries has a range of information available about ICOLLs and their management. The state governmental also has a short video explaining ICOLL management here.