Meeting Date: Wednesday, 31 March 2021
Location: Council Chambers, City Administrative Centre, Bridge Road, Nowra
The following members were present:
Clr Patricia White – Chairperson
Clr Kaye Gartner
Clr Nina Digiglio
Holly Gunton – (remotely)
David Laidlaw – (remotely)
John Murtagh – Department of Planning, Industry and Environment (remotely)
William McInnes – Flood Planning Ulladulla SES (remotely)
Julian Skipworth, Water Modelling Solutions – (remotely)
Phil Hansen – Acting Manager, Environmental Services
Mark Stone – Senior Floodplain Engineer
Tanvir Ahmed – Floodplain Engineer
Apologies were received from Adam Crossley, Tracy Provest (SES) and Rodney Feltham (SES).
That the Minutes of the Southern Floodplain Risk Management Committee held on Wednesday 25 November 2020 be confirmed.
HPERM Ref: D21/118892
John Murtagh, Department of Planning, Industry and Environment (DPIE), gave a presentation on Floodplain Risk Management in the context of the Shoalhaven, and the role of the Committee. The presentation was based on that given at the previous meeting on 25 November 2020, with updates, and is attached to these minutes.
HPERM Ref: D21/118896
· Princes Highway at Millards Creek inundated in fairly frequent events but to shallow depths.
· Piped Sections of waterway between Warden St and Spencer St, overtopped in 20% AEP event and higher. In 1% AEP event becomes very significant and hazardous.
· Ulladulla High School overland flowpaths evident in larger events; hazard remains low.
· Several areas where roadways become significant flowpaths (Princes Highway, St Vincent St, (Burrill St South).
· Several areas where roadways become overtopped in 1% AEP event (Croft Ave, Village Drive)
· Deeper inundation is generally well confined to waterways
· Risk to property is generally quite low other than some small pockets
· Some roads are overtopped and access is cut; however there are a few residential areas which become isolated.
· Sea level rise has minimal impact on flood risk on this catchment; impacts don’t extend beyond the harbour and lower estuary.
Julian confirmed the magnitude of the most recent flood event (March 2021) has not yet been investigated. He advised the depth of rainfall was expected to be less than the 2013/14 events that this model was calibrated to.
Developments since 2013-14:
Mark Stone (Senior Floodplain Engineer) advised there has been some recent development in the upper part of the catchment, but onsite detention is required by Council policy.
The implementation of onsite detention in future developments will prevent the magnitude of flood events increasing beyond that estimated by this flood study.
HPERM Ref: D21/93006
Mark Stone, Senior Floodplain Engineer, presented the Draft Millards Creek Flood Study. The presentation was to be circulated to members.
The report has been completed and feedback has been provided by Council, DPIE and SES. The next step in the project programme is community consultation and public exhibition, planned from 12 April to 7 May 2021. The outcomes from the community consultation and public exhibition will be reported to another Floodplain Risk Management Committee meeting which will seek endorsement for Council to adopt the Millards Creek Flood Study.
Clr Gartner asked whether some of the mitigations under the changes to the DCP would assist with insurance costs. Mark Stone advised this information would not be readily available to be part of the consultation. John Murtagh (DPIE) noted it would be difficult for Council to determine what the insurance industry’s response would be; this would be a useful discussion to have with the Insurance Council of Australia.
The Committee receive the Draft Millards Creek Flood Study report for information and endorse the commencement of community engagement for the Draft Flood Study.
That the Committee receive the Draft Millards Creek Flood Study report for information and endorse the commencement of community engagement for the Draft Flood Study.
Clr White asked about the recent floods in the Nepean River area. John Murtagh explained the impacts varies according to location. At Penrith the floods seemed larger. At Hawkesbury and at Windsor the event was in the ballpark of 10% to 5% AEP. All the flood events appear comparable until they approach very large, 1% AEP and above events. The analysis John has seen to date indicates it had not been a significantly large event at Windsor, but there were significant impacts further up the catchment, e.g. Picton, Camden. He has not yet seen analysis of the North Coast events, but he understood them to be in the 2% and above range.
John agreed the Lower Shoalhaven River can be subject to very extensive flooding. He will bring any analysis to Mark Stone for a future meeting of the committee.
Additional information is attached to these minutes.
Bill McInnes (SES) expressed gratitude to Council staff and DPIE staff for their information and rapid responses to his questions.
That the Committee thank the Council staff and DPIE for their work during the heavy rainfall events in March.
There being no further business, the meeting concluded, the time being 5.28pm.
Clr Patricia White