We have bushland catchments in the west and north of Warringah, and beach catchments in the east.
Our bushland catchments flow into Middle Harbour and the Hawkesbury River. Warringah's western catchment covers 2,478ha and includes five sub-catchments which flow into Middle Harbour. The sub-catchments are Bare Creek in Belrose, Frenchs Creek and Carol Creek in Davidson and Killarney Heights, and Bantry Bay in Forestville and Frenchs Forest. Approximately 50% of the Middle Harbour catchment is bushland, mostly within the Garigal National Park.
Warringah’s northern catchment covers 5,678ha and includes five sub-catchments which flow into Cowan Creek, then into the Hawkesbury River. The sub-catchments of Kieran’s Creek, Duffys Creek, Smiths Creek, McCarrs Creek and Cottage Point are primarily located in the suburbs of Terrey Hills, Duffys Forest and Cottage Point. A significant portion of the northern catchment is located in Ku-ring-gai National Park, with over 87% bushland making this catchment one of the most pristine in Sydney!
Even though these catchments have a lot of bushland, the areas at the top (the suburbs of Terrey Hills and Duffys Forest in Cowan catchment; Bantry Bay, Forestville, Killarney Heights, Frenchs Forest, Belrose and Davidson in Middle Harbour catchment) are developed. These upper areas of the catchment have a significant impact on the quality of the water in the creeks, as weeds, sediments and pollutants can enter the upper reaches of the creeks and cause problems all the way downstream.
In Duffys Forest, where creeks are generally on private property, our landholders have a special responsibility to protect their creeks from the impact of any development on their property.
Some of Warringah’s smaller catchments flow directly into our ocean beaches, including the Narrabeen Beach foreshore and Collaroy Beach catchments. These cover approximately 256ha and 204ha respectively, with over 70% used for residential land use purposes.
The Dee Why Beach catchment covers close to 59ha and Freshwater Beach catchment about 107ha. These catchments have the highest proportion of residential land use in Warringah with approximately 89%.
Heavily urbanised catchments are characterised by extensive amounts of hard surfaces (carparks, roads, roofs) which collect and transport stormwater directly to the ocean rather than allowing it to slowly soak into the soil. This means that stormwater pollution is more likely. People living in these catchments need to be particularly aware that whatever enters the stormwater drain could end up on the beach.