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.
Where are we now? (March 2022)
A report was presented to Council at the meeting held Tuesday 22 March 2022 with the outcomes of the public exhibition of the draft feasibility study and to consider the next steps for this project.
During the meeting Council endorsed immediately progressing with detailed design and environmental assessments for reducing flooding at the Oxford Falls and Oxford Falls Road west sites.
Given the community concern regarding environmental impacts, it was also decided to review options at The Bends site to determine if the impact could be reduced further. This work is underway.
It is important to remember that this work is targeting the smaller more frequent road closures associated with Council’s creeks and drainage. The more significant flood improvements such as bridges, raising the road or widening which were suggested by some during the consultation period, are a matter for the NSW Government who own and manage this roadway.
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Flood improvements for Wakehurst Parkway
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.
About Wakehurst Parkway
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:
- Red-crowned Toadlet.
- Giant Burrowing Frog.
- Eastern Osprey.
- Glossy Black Cockatoo.
- Varied Sittella.
- Black Bittern.
- Powerful Owl.
- Sooty Owl.
- Little Bentwing-bat.
- Eastern Bentwing-bat.
- Eastern Freetail-bat.
- Southern Myotis.
- Grey-headed Flying-fox.
- Large-eared Pied Bat.
- 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).
Short listed options across the three sites
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Photo credit: UNSW Water Research Laboratory - Chris Drummond