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AGENDA R |
Flood Management Advisory Committee Meeting
THURSDAY 12 DECEMBER 2019
4.00pm
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Flood Management Advisory Committee Meeting 12 December 2019 |
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AGENDA |
1 Apologies
2 Disclosures of Interest
3 Confirmation of Minutes
Minutes of 28 March 2019 Flood Management Advisory Committee Meeting 4
4 Staff Reports
ITEM PAGE #
FMACC1219 Item 1
Presentation of the Final Dobroyd Canal and Hawthorne Canal Flood Risk Management Study and Plan 10
5 General Business
6 Close of Meeting
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Flood Management Advisory Committee Meeting 12 December 2019 |
Minutes of Meeting
Thursday 28th March 2019
Ashfield Administration Centre Meeting Room 1
Level 6, 260 Liverpool Rd Ashfield
Meeting commenced at 3.05pm
ACKNOWLEDGEMENT OF COUNTRY BY CHAIRPERSON
Acknowledgement of Country by Clr Marghanita Da Cruz
I would like to acknowledge the Gadigal and Wangal peoples of the Eora nation who are the traditional custodians of this land. I would also like to pay respect to Aboriginal Elders, past and present, and acknowledge their young people who will be our future leaders.
COMMITTEE REPRESENTATIVES PRESENT
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Voting Members |
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Inner West Council |
Clr Marghanita Da Cruz (Chair) |
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State Emergency Service |
Alexander Bailey |
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State Emergency Service |
Robert Baker |
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Community Representative |
Lois Gray |
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Community Representative |
Shad Wall |
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Non-voting Technical Advisory Members |
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Inner West Council |
Wal Petschler |
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Inner West Council |
Tony Giunta |
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Inner West Council |
James Ogg |
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Inner West Council |
David Birds |
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Inner West Council |
Jai Read |
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NSW Office of Environment & Heritage |
Sadeq Zaman |
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NSW State Emergency Service |
Klaus Neuscheler |
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NSW State Emergency Service |
Pilar Lorenzo |
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Sydney Water |
David Grasby |
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NSW Roads and Maritime Services |
Ashraf Awadalla |
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Burwood Council |
Pablo Barreto |
APOLOGIES
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Inner West Council |
Clr Lucille Mckenna OAM |
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Inner West Council |
Clr Colin Hesse |
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Community Representative |
Tim Harnett |
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Community Representative |
Lindy Junkari |
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Inner West Council |
Elizabeth Richardson |
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Inner West Council |
Joe Di Cesare |
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Inner West Council |
Cathy Edward-Davis |
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Inner West Council |
Jan Orton |
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Inner West Council |
Harjeet Atwal |
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Inner West Council |
Jean Brennan |
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NSW Office of Environment & Heritage |
Greg Davis |
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NSW Department of Primary Industries |
Carla Ganassin |
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NSW State Emergency Service |
George Jeoffreys |
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NSW State Emergency Service |
Daniel Walker |
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NSW Roads and Maritime Services |
Mark Millington |
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NSW Roads and Maritime Services |
Susannah Webb |
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City of Sydney |
Peter Garland |
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City of Sydney |
Shah Alam |
TERMS OF REFERENCE
The Committee is advisory in nature and any recommendations are not binding on Council. The Committee currently has nine voting members of which five voting members were present, satisfying a quorum of 50% for the meeting.
DISCLOSURES OF INTERESTS:
Nil declared
CONFIRMATION OF MINUTES
Minutes of the previous meeting held 14 December 2017 were accepted as correct.
Committee Recommendation:
THAT the minutes of the previous Flood Management Advisory Committee meeting be noted and accepted.
For Motion: Unanimous.
MATTERS ARISING
· Committee was advised that Council had been unsuccessful in obtaining interagency cooperation from WestConnex and Metro projects to consider a gravity line drainage solution, proposed by Council, as part of their works to connect intersection of May/ Campbell streets St Peters directly to the Eastern Channel.
STAFF REPORTS
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FMACC0319(1) Item 1 Presentation of the Draft Dobroyd Canal and Hawthorne Canal Flood Risk Management Study and Plan |
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RECOMMENDATION
THAT the Draft Hawthorne Canal and Dobroyd Canal Flood Risk Management Study and Plan dated March 2019 be endorsed for community engagement.
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The Committee was presented with an overview of the background and context behind the Dobroyd Canal and Hawthorne Canal Floodplain Risk Management Study and Plan. The Plan recommends projects within three broad areas - property modification, response modification and flood modification.
A total of fifty-six potential options were reduced to six after a high level assessment that removed options that had no flood change, negative cost-benefit, or significant technical constraints. Options to proceed to Community Engagement include:
i. Underground detention basins at Pratten Park and Arthur Street Tennis Courts
The installation of detention basins would reduce depths by up to 0.15m between Pratten Park and the railway and remove property inundation above the floor level for 42 properties in the event of a 1% AEP event. Some challenges for this option include property ownership and short-term disruption to the playing field.
ii. Grosvenor Crescent and Smith Street flowpath pipe upgrade and detention basin
Involves an upgrade to the existing pipeline beneath the rail embankment draining Grosvenor Crescent, and the installation of a dam wall within Darrell Jackson Gardens to create a detention basin within the park. This would result in a reduction of property inundation for four properties, as well as a reduction in some road inundation. Substantial reduction in ponding depths also achieved in Grosvenor Crescent in smaller scale storms.
iii. Nowranie Street to Hawthorne Canal Pipe Upgrade
This option proposes a 1.2m diameter pipeline from Morris Street and extending to Smith Street, before discharging to Hawthorne Canal. This option has a relatively high benefit-cost ratio, and reduces flood depths for the extent of the upgrade by up to 0.5m, however only reduces dwelling inundation for three properties in the 2% AEP event.
iv. Petersham Park Above Ground Detention Basin
This option can achieve reductions in flood depths between Petersham Park, Parramatta Road and Hawthorne Canal by up to 0.5m. The study identified that only three properties within the study area would however accounting for the properties within Leichhardt, the Benefit-Cost Ratio is likely to be significantly higher.
The Flood Risk Management Study will be amended prior to being put on public exhibition to include the benefit to properties north of Parramatta Road.
Existing Heritage concerns and protected Bandicoot species within this park was noted. This will be accommodated within the multi-criteria assessment and continued review of the mitigation program as it is rolled out.
v. Sloane Street Pipe Upgrade
This option would reduce depths by approximately 0.3m and provide a reduction in property inundation for five properties.
vi. Waratah Street to City West Link Hawthorne Canal Levee
This option was included within the draft report as it had high community interest, due to recurrent flooding from rising tides. This option however showed little impact on tidal heights and actually expanded the flood affected area and increased levels behind the levee by up to half a metre.
It is recommended that this option be removed from the plan given the high detrimental impacts, and included within the Appendix with the other discounted options.
The committee concurred with this assessment, however recommended that this option be discussed within a separate section of the report.
Questions & Discussions Regarding Report:
Issues raised by Committee Members included:
It was noted that WSUD acts in a complimentary manner with Flood Mitigation. Effective WSUD infrastructure is best utilised in the smaller more frequent rain events. It is noted that the proposed options do not preclude the construction of future WSUD components, and there would likely be capacity to incorporate construction of select WSUD elements as part of the infrastructure upgrade.
The Flour Mills site had not commenced construction at the time that the model was reviewed. Therefore the model does not show impacts caused by this development. The approved development was required to comply with Council’s Flood Risk Development Controls including management and mitigation of flooding within the site. Existing flood behaviour around the site is generally maintained as modelled.
The exact alignment and construction techniques for each option would be confirmed as they progress to detailed design. The current options have been chosen to minimise the potential for conflict with site constraints.
Flow valves were installed 18 months ago to prevent backflow from the canal; however the valve has not been performing to specification and Council is currently pursuing rectification.
Council would liaise with the relevant agencies (such as RMS, Sydney Water, OEH or adjacent Councils) to negotiate/ apply for potential funding contribution.
The site has been previously identified as a flood affected property. There is an existing consent to divide and develop the land with new dwellings within this flood affected area. The development consent required stormwater works were undertaken as part of the initial development, with further works still to be undertaken in O’Conner Street. In addition, the new properties would still be subject to some degree of flooding in the design event, and would be required to meet current development controls with regard to safe floor levels and provision of flow paths through the property.
This site is contained within the Leichhardt Flood Risk Management Study and Plan, previously adopted by Council in 2018. It was noted that Canal Road was a trapped low point created in the construction of City West Link in order to maintain sufficient headroom clearance beneath the rail embankment for truck entry and exit from Canal Road. This pipe frequently blocks and Council is reviewing the source of this blockage and any potential improvements.
Traffic congestion is generally considered a factor that must be considered in emergency management planning led by SES.
New developments have specific controls that require all accesses to basements to be raised above the design flood level before descending below ground. This typically ensures that the basement is isolated from the surface flood waters. Supplemented with site flood management plan.
COMMITTEE RECOMMENDATION:
THAT: The report be endorsed and Council progress to community engagement subject to the following:
- The Cost-Benefit assessment of Petersham Park (Option 4) be amended to include reductions in flood damage north of Parramatta Road
- That the proposed levee along Hawthorne Canal (Option 6) not be supported and discussed in an addendum to the report only.
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For Motion: Unanimous.
GENERAL BUSINESS
1. Progress on investigations into upgrade / naturalisation of Whites Creek.
The committee has previously been advised on potential works within Whites Creeks to renew existing canal walls and the covered culvert. Whites Creek can be considered in terms of two separate sections
- A covered channel between Parramatta Road and Booth Street
- An open channel between Booth Street and Rozelle Bay
Sydney Water’s renewal schedules, based on condition assessment, do not necessarily require upgrade for flood conveyance. However it has been noted in the Leichhardt Flood Risk Management Plan that the surrounding stormwater network will continue to have poor flood performance if maintained at the existing capacity.
The most recent advice to Council from Sydney Water was that any works within Whites Creek were not scheduled for the near future. Council will continue discussions about potential upgrade designs which can support additional upgrade funding when it does come time to renew the relevant sections of the canal.
2. State Emergency Services Changes
SES advised that the existing Sydney West Region SES has been incorporated into metropolitan region. For flood responses in some instances the distance to travel has become further now, given the greater response area, so early warning time assists greatly in proper allocation of resources.
Increasing community awareness plays a significant part in flood response. Marrickville SES had practiced street meets at known flooding hotspots, discussing expectations with new volunteers, and further raising community awareness.
3. Progress of remaining Flood Studies across Inner West Council.
Council had applied for and was successful in receiving grants from the Office of Environment and Heritage for the following projects;
- Whites Creek and Johnsons Creek Flood Risk Management Study and Plan
- Alexandra Canal Flood Risk Management Study and Plan
- Marrickville South Flood Study
Council intends to commence these studies in the second half of 2019.
Meeting closed at 4:55pm.
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Flood Management Advisory Committee Meeting 12 December 2019 |
Subject: Presentation of the Final Dobroyd Canal and Hawthorne Canal Flood Risk Management Study and Plan
Prepared By: James Ogg - Stormwater and Development Engineer
Authorised By: Cathy Edwards-Davis - Director Infrastructure
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RECOMMENDATION
THAT:
That the Flood Management Advisory Committee endorse the final draft Dobroyd Canal and Hawthorne Canal Flood Risk Management Study and Plan to Council for adoption.
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DISCUSSION
At the meeting of the Flood Risk Management Advisory Committee dated 28 March 2019, the committee voted to endorse the draft Dobroyd Canal and Hawthorne Canal Flood Risk Management Study and Plan for public exhibition.
The draft Dobroyd Canal and Hawthorne Canal Flood Risk Management Study and Plan was placed on public exhibition for a period of 5 weeks from the 22nd July 2019 to the 30th August 2019. The exhibition was coordinated through Council’s Your Say Inner West community engagement page, with additional support via notification in the Inner West Courier and Council’s Social Media channels. Letters of notification were also extended to owners of properties identified as Flood Affected Properties.
During the public exhibition period, the community members and interested parties were invited to review the study and plan, submit comments, and indicate the extent of their support for the study, plan and its outcomes. Community members were also able to provide comment on which options they support, which options they do not support and any matters related to flood mitigations and management that had not been addressed in the study and plan.
Four community workshops were held during the public exhibition period to present the findings of the study and plan and seek input from the community. The workshops were held at the Ashfield Civic Centre on 13th and 14th August and at the Yanada Room at Petersham on 20th and 21st August.
During the exhibition period the webpage was visited 541 times and project documents were downloaded 187 times. A total of thirteen submissions were received through the Council’s website. Of these submissions, eight were overall supportive of the plan and five were not supportive of the plan. Of these five two submissions had specific concerns with regard to a lack of options on Fred Street, which was reviewed and incorporated into the Final Plan. A third submission had concerns about the accuracy of the study and the impact of WestConnex. The concerns of these submissions were adequately addressed during the information sessions or by the amended report. Only two submissions remained not supportive of the plan.
A summary of submissions received and responses to those submissions are provided in Appendix G of the final Dobroyd Canal and Hawthorne Canal Flood Risk Management Study and Plan.
Internal feedback was also requested and received from Council’s Development Advisory Service and Urban Ecology teams.
Council’s Development Advisory Service raised concerns that several of the Flood Modification options require works in and around listed Heritage items and within identified Heritgage Conservation Areas. Further detail would be required as part of any further assessment of a detailed design.
The Urban Ecology team noted that an upstream section of Hawthorne Canal is contained within the Bandicoot Protection Area identified in the Marrickville DCP 2011. It is noted that any proposed works, included the proposed detention basin within Petersham Park would need to consider further environmental impact assessment as part of the detailed design, addressing both the built environment (heritage) and natural environment (ecology).
Based on the submissions received, Council has included an additional Flood Mitigation option within Old Canterbury Road. The remaining additional scenarios that did not generate a substantial benefit, were incorporated into the relevant appendices.
FINANCIAL IMPLICATIONS
The draft report recommends five infrastructure upgrade projects at a total cost to Council of $17.2 million.
These projects will be progressively incorporated into the future works program as opportunity and funding are available.
