Creeks and Lagoons

Much of the rain that falls in the Warringah flows into our creeks and lagoons. We use the term ‘catchment’ to describe the area that collects this rainfall. Warringah Council works hard to protect its water catchments and in doing so maintain and enhance the quality of the water in our creeks and lagoons.

• Creeks
• Lagoons
• Manly Lagoon Dredging Project

Manly Lagoon Dredging Project Completed

Manly and Warringah Councils, in association with the NSW Office of Environment and Heritage, have completed dredging works at Manly Lagoon. More on the Manly Lagoon Dredging Project.

 

Creeks

Warringah has over 50km of creeks in six major catchments. The creeks range in condition from near pristine bush creeks to heavily modified urban streams. The largest creek systems are South Creek, Deep Creek, and Middle Creek, which are in the Narrabeen Lagoon catchment, and occupy about 40% of Warringah’s area. The creeks that drain to Dee Why, Curl Curl and Manly lagoons cover catchments that are approximately 30% of Warringah’s area, while the remaining 30% is made up of six small sub-catchments that drain to either Cowan Creek (Hawkesbury River) or Middle Harbour.

Many of these creeks have been heavily impacted by the development of their once natural bush catchments, into houses, roads and businesses. The increase in hard surfaces means that more water runs off the catchment into the creeks. Stormwater pipes collect this water and transfer it at much higher speeds than would happen in nature and can cause problems with flooding and also erode streambanks. In a natural catchment, vegetation helps to reduce the amount of pollutants travelling downstream. In a developed catchment this important pollutant trap has been lost. Artificial structures like roads, culverts and bridges can also create barriers for fish and animals that use the creeks. One of the biggest threats to our creeks are weeds, which choke creeklines and can outgrow and smother native creek vegetation which are important homes for native animals. In some circumstances, they can also pose a flooding risk.

Warringah Council's Creek Management Study, March 2004

• Creek Management Study - complete (PDF, 118MB)
• Appendix A Study Methodology (PDF, 53KB)
• Appendix B 1 Kierans Creek (PDF, 1.9MB)
• Appendix B 2 Duffys Creek (PDF, 1.9MB)
• Appendix B 3 Greendale Creek (PDF, 4.3MB)
• Appendix B 4 Dee Why Creek (PDF, 4MB)
• Appendix B 5 Brookvale Creek (PDF, 6.3MB)
• Appendix B 6 Manly Creek (PDF, 5.1MB)
• Appendix B 7 Burnt Bridge Creek (PDF, 3MB)
• Appendix B 8 Bare Creek (PDF, 2.7MB)
• Appendix B 9 Frenchs and Carroll Creeks (PDF, 5.8MB)
• Appendix B 10 Bantry Bay (PDF, 2.6MB)
• Appendix B 11 Deep Creek (PDF, 1.9MB)
• Appendix B 12 Middle Creek (PDF, 8.1MB)
• Appendix B 13 Oxford Creek (PDF, 3.8MB)
• Appendix B 14 South Creek (PDF, 6.9MB)
• Appendix B 15 Wheeler Creek (PDF, 2.5MB)
• Appendix B 16 Narrabeen Foreshores (PDF, 2.7MB)
• Appendix B 17 Collaroy Creeks (PDF, 1.7MB)
• Appendix B 18 Reach Risk Analysis (PDF, 157KB)
• Appendix B 19 Reach Risk Analysis (PDF, 86KB)
• Appendix C Preliminary Heritage Advice (PDF, 307KB)
• Appendix D Riparian Zones and Buffers Disscussion Paper (PDF, 46KB)
• Appendix E Sustainable Waterway Management and the LEP (PDF, 140KB)
• Appendix F  Planning, Design and Operational Guidelines (PDF, 87KB)
• Appendix G Summary Analysis and River Styles in the War (PDF, 27KB)
• Appendix H Breakdown of Implementation Plan Costs by P (PDF, 13KB)
• Appendix H Breakdown of Implementation Plan Costs by R (PDF, 13KB)
• Appendix I Heirarchical Numbering System (PDF, 9KB)

Lagoons

There are four coastal lagoons (or estuaries) along the Warringah coast. Narrabeen Lagoon is jointly managed with Pittwater Council and Manly Lagoon is jointly managed with Manly Council. Dee Why and Curl Curl Lagoons are managed solely by Warringah Council.

The entrances of these lagoons naturally open and close depending on rainfall and ocean conditions. They are home to a wide variety of plants and animals which are especially adapted to cope with a mix of freshwater and saltwater conditions. Too much freshwater can damage the system, and too much ocean water can damage the system. Council tries to maintain this delicate balance which is complicated by stormwater pollution and unauthorised lagoon openings.

The area of hard surfaces (roofs and roads) in the catchment has increased with urban development. These hard surfaces don’t absorb rainfall like soil and plants do, which creates more runoff into our lagoons. This runoff and the presence of houses close to the lagoons can create a risk of localised flooding. Council manages this small-scale flooding by opening the entrances to the lagoons periodically to alleviate the problem. While this is at times necessary, Council together with the NSW Department of Natural Resources and the NSW Department of Primary Industries (Fisheries) allows the lagoons to open naturally as much as possible.

For more information on which catchment you live in, or to find out more about the lagoons and creeks in Warringah, contact Council on 9942 2111.