Wakehurst Parkway is one of the main road connections on the Northern Beaches passing through Narrabeen, Oxford Falls, Frenchs Forest, and North Balgowlah.

While an important thoroughfare for our community, the areas surrounding Wakehurst Parkway (the Parkway) have significant cultural heritage and environmental values associated with the adjoining bushland and riparian areas.

Local residents will be aware that the Parkway north of Warringah Road is prone to flooding in certain areas and has historically experienced frequent road closures as a result. At present, this is up to six to seven times per year on average. Check out the overview of the key drivers of flooding for more information.

The draft Wakehurst Parkway Flood Mitigation Feasibility Study (draft feasibility study) was completed with grant funding through the NSW Government Stronger Communities Fund to explore options to help protect the road from flooding.

In March 2022 Council resolved to progress the detailed design and environmental assessments for the culvert upgrades at Oxford Falls and review the options at The Bends to try and reduce the environmental impact in response to community feedback. A significant amount of design work has been undertaken, and Council is working with stakeholders around complexities of the project sites.

At Oxford Falls works are progressing on the design and planning approvals for culvert upgrades. Site investigations have been undertaken including survey, services location, geotechnical and contamination investigations. A preliminary design is in development and a draft Review of Environmental Factors (REF) has been prepared. Council is currently working with TfNSW to confirm all required design criteria. Council is also working with Jemena to resolve potential design impacts from a high-pressure gas main in the vicinity of the works. The outcome of these discussions will impact how and when the works progress.

We will come back to the community with an updated timeline and draft Review of Environmental Factors for the Oxford Falls works when these design requirements have been resolved.

At The Bends, a panel of experts have reviewed the Feasibility Study designs, and additional modelling of improved options has been undertaken. A revised design is being developed to try and reduce the area of vegetation clearing. Council is working with TfNSW to understand their design requirements for the site and securing funding commitments.

Staff are continuing to discuss and finalise funding arrangements and priorities with TfNSW.

The draft feasibility study explored options to address key problem flooding sites along the Parkway outlining indicative costs and potential environmental considerations. The options were evaluated across four potential levels of flood protection.

We developed a comparison table showing the effectiveness, and potential constraints and impacts of each option to achieve different levels of flood improvement for the Parkway.

Based on the findings within the draft feasibility study the most effective solution to manage frequent flooding would be to implement the combination of options B4, O2 and S1 (as outlined in the comparison table). These options are designed so that the Parkway (north of Warringah Road, would only close in storm events exceeding a 1 in 2 year Average Recurrence Interval (ARI). However these options result in significant environmental impacts.

Transport for New South Wales (TfNSW) has agreed to provide additional funds that allow us to implement the above options as a project, should Council decide to proceed.

If this project progresses past the current stage, further environmental investigations, project planning, detailed design and delivery would all need to be undertaken.

This project, if it proceeds, is expected to have environmental impacts which will be assessed in the next stage of the project. Council is committed to exploring ways to ensure the local and unique ecological character of the Middle Creek catchment and the Parkway area is appropriately rehabilitated and maintained into the future.

Wakehurst Parkway is a state-owned arterial road and popular commuter route in the Northern Beaches. The Parkway runs through an area of high environmental significance.

An important connection

The Parkway serves as a key route for commuters travelling to and from the Sydney and Parramatta CBDs and key commercial districts including Chatswood and North Sydney in the morning and evening weekday peaks (linking drivers eventually with the Pacific Highway to the west and Pittwater Road to the south and east). It also acts as a key transport link in the area providing an alternative connection to using Mona Vale and Pittwater Roads.

The Parkway north of Warringah Road is prone to flooding, with road closures typically six to seven times a year. This frequent flooding typically occurs when Middle Creek’s floodplain fills up, triggered by heavy rainfall. TfNSW estimate 8,000 trips daily on average depending on time of day and week, and an average road closure of around five hours. During flood events, this can impact hundreds of drivers an hour.

An environmental and culturally sensitive area

The riparian corridor in the Creek is recognised as Key Fish Habitat by the Department of Primary Industries (DPI). Seven different plant community types are found in the area, including threatened ecological communities (TECs), and the set of options has the potential to affect four habitats identified as TECs under the Biodiversity Conservation Act 2017.

Fifteen threatened fauna species were found to likely use the environment between the Parkway and Middle Creek as foraging habitats. These are:

1. Red-crowned Toadlet.
2. Giant Burrowing Frog.
3. Eastern Osprey.
4. Glossy Black Cockatoo.
5. Varied Sittella.
6. Black Bittern.
7. Powerful Owl.
8. Sooty Owl.
9. Little Bentwing-bat.
10. Eastern Bentwing-bat.
11. Eastern Freetail-bat.
12. Southern Myotis.
13. Grey-headed Flying-fox.
14. Large-eared Pied Bat.
15. Rufous Fantail - migratory under the Environmental Protection and Biodiversity Conservation Act 1999 (EPBC).

Overview of environment considerations

The Parkway is prone to flooding

The Parkway north of Warringah Road is prone to flooding with road closures typically six to seven times a year. This frequent flooding occurs when Middle Creek's floodplain fills up, triggered by heavy rainfall.

The maps below shows the three sites along the Parkway that have been found to be more flood-prone. The options in the draft feasibility study target these sites in order to reduce flooding.

Overview of flooding along the Parkway

Options assessment process

Over a period of several years, TfNSW and Council have investigated flooding along the Parkway.

With funding from the NSW Government Stronger Communities Fund, Council commissioned investigations to:

• understand the nature and key drivers of flooding on the Parkway
• understand potential options that could be implemented
• assess and understand the impacts of these options.

Investigations were conducted in phases with the initial data collection taking place over 2017 to 2018 and further detailed assessments happening in 2019. These informed an options assessment process, which included identification and assessment of a long list of options, and two rounds of shortlisting.

Council wrote to TfNSW to seek additional funding in December 2019. A formal funding offer from TfNSW to proceed was received in February 2021. Since then, Council finalised the draft feasibility study, presented it to the elected Council in March 2021 and placed it on public exhibition for 52 days.

The figure below provides a snapshot of the options assessment process with an overview of the options that were considered feasible to progress and those that were excluded at each stage (indicated by strike-through text).

The full list of investigations can be found in Section 3 of the draft feasibility study.

Photo credit: UNSW Water Research Laboratory - Chris Drummond