Narrabeen Lagoon Entrance Management

 The entrance to Narrabeen Lagoon can become periodically filled with marine sediment when the amount of sand moved into the lagoon entrance from the beach by the incoming tide continually exceeds the amount of sand removed by the outgoing tide. The closure of the lagoon entrance for extended periods can have significant socio-economic and environmental impacts on the lagoon and surrounding areas, including:

• Increases in the severity of flooding of low lying residential/commercial areas surrounding the lagoon, as well as creeks discharging into it;
• Reductions in lagoon water quality due to impaired tidal flushing from the entrance;
• Decrease in biodiversity due to reduced recruitment through the entrance.

In order to manage this dynamic system and reduce the risk of flooding, Warringah and Pittwater Councils, with the assistance of the NSW Government under its Floodplain Management Program, periodically undertake clearance operations.  This work is part of the management actions in the adopted Floodplain Risk Management and Estuary Management Plans for Narrabeen Lagoon and the adopted Coastline Management Plan for the Collaroy-Narrabeen embayment. 

Since 1975, the clearance operations have been undertaken approximately every three years. The cleared sand from the entrance is placed on Collaroy/Narrabeen Beach which has a long history of coastal erosion.

 

Further information

The LagoonWatch computer system provides real time information on tides, water levels, offshore wave height, rainfall and stream-flow in addition to providing a predictive model for future entrance and flood conditions. Readers interested in viewing the LagoonWatch website should click on the link.

Further information on entrance clearance operations is available in a paper by Cameron et al (2007) titled ‘Management and Monitoring of an ICOLL Entrance Clearance’, and presented at the 17th NSW Coastal Conference.

A Review of Environmental Factors was completed in February 2011 as part of the planning stage for the next entrance clearance operation.

Current Status

More information on the current status of the Narrabeen Lagoon Entrance.

For enquiries about the management of the entrance of Narrabeen Lagoon contact:

Valerie Tulk or Daylan Cameron
Natural Environment Unit
Ph 9942 2111